Create, Edit, or Compose Bitmap Images With These Command-line Options

-adaptive-blur radius[xsigma]

-adaptive-resize geometry

-adaptive-sharpen radius[xsigma]

-adjoin

-affine s_x,r_x,r_y,s_y[,t_x,t_y]

-alpha type

-annotate degrees text
-annotate XdegreesxYdegrees text
-annotate XdegreesxYdegrees {+-}t_x{+-}t_y text

-antialias

-append

-attenuate value

-authenticate password

-auto-gamma

-auto-level

-auto-orient

-average

-backdrop

-background color

-bench iterations

-bias value{%}

-black-point-compensation

-black-threshold value{%}

-blend geometry

-blue-primary x,y

-blue-shift factor

Convolve the image with a Gaussian or normal distribution using the given Sigma value. The formula is:

The Sigma value is the important argument, and determines the actual amount of blurring that will take place.

The Radius is only used to determine the size of the array which will hold the calculated Gaussian distribution. It should be an integer. If not given, or set to zero, IM will calculate the largest possible radius that will provide meaningful results for the Gaussian distribution.

The larger the Radius the slower the operation is. However too small a Radius, and sever aliasing effects may result. As a guideline, Radius should be at least twice the Sigma value, though three times will produce a more accurate result.

This option differs from -gaussian-blur simply by taking advantage of the separability properties of the distribution. Here we apply a single-dimensional Gaussian matrix in the horizontal direction, then repeat the process in the vertical direction.

The -virtual-pixel setting will determine how pixels which are outside the image proper are blurred into the final result.

Each pixel in the overlaid region is replaced with an Elliptical Weighted Average (EWA) of the source image, scaled according to the grayscale mapping.

The ellipse is weighted with sigma set to the given Width and Height. The Height defaults to the Width for a normal circular Gaussian weighting. The Angle will rotate the ellipse from horizontal clock-wise.

The -virtual-pixel setting will determine how pixels which are outside the image proper are blurred into the final result.

Set the width and height using the size portion of the geometry argument. See Image Geometry for complete details about the geometry argument. Offsets are ignored.

Set the border color by preceding with the -bordercolor setting.

The -border operation is affected by the current -compose setting and assumes that this is using the default 'Over' composition method. It generates a image of the appropriate size colors by the current -bordercolor before overlaying the original image in the center of this net image. This means that with the default compose method of 'Over' any transparent parts may be replaced by the current -bordercolor setting.

See also the -frame option, which has more functionality.

The color is specified using the format described under the -fill option.

The default border color is #DFDFDF, this shade of gray.

Brightness and Contrast values apply changes to the input image. They are not absolute settings. A brightness or contrast value of zero means no change. The range of values is -100 to +100 on each. Positive values increase the brightness or contrast and negative values decrease the brightness or contrast. To control only contrast, set the brightness=0. To control only brightness, set contrast=0 or just leave it off.

You may also use -channel to control which channels to apply the brightness and/or contrast change. The default is to apply the same transformation to all channels.

Brightness and Contrast arguments are converted to offset and slope of a linear transform and applied using -function polynomial "slope,offset".

The slope varies from 0 at contrast=-100 to almost vertical at contrast=+100. For brightness=0 and contrast=-100, the result are totally midgray. For brightness=0 and contrast=+100, the result will approach but not quite reach a threshold at midgray; that is the linear transformation is a very steep vertical line at mid gray.

Negative slopes, i.e. negating the image, are not possible with this function. All achievable slopes are zero or positive.

The offset varies from -0.5 at brightness=-100 to 0 at brightness=0 to +0.5 at brightness=+100. Thus, when contrast=0 and brightness=100, the result is totally white. Similarly, when contrast=0 and brightness=-100, the result is totally black.

As the range of values for the arguments are -100 to +100, adding the '%' symbol is no different than leaving it off.

This option sets the caption meta-data of an image read in after this option has been given. To modify a caption of images already in memory use "-set caption".

The caption can contain special format characters listed in the Format and Print Image Properties. These attributes are expanded when the caption is finally assigned to the individual images.

If the first character of string is @, the image caption is read from a file titled by the remaining characters in the string. Comments read in from a file are literal; no embedded formatting characters are recognized.

Caption meta-data is not visible on the image itself. To do that use the -annotate or -draw options instead.

For example,

-caption "%m:%f %wx%h" bird.miff

produces an image caption of MIFF:bird.miff 512x480 (assuming that the image bird.miff has a width of 512 and a height of 480.

Here is an example color correction collection:

<?xml version="1.0" encoding="UTF-8"?>
<ColorCorrectionCollection xmlns="urn:ASC:CDL:v1.2">
  <ColorCorrection id="cc06668">
    <SOPNode>
      <Slope> 0.9 1.2 0.5 </Slope>
      <Offset> 0.4 -0.5 0.6 </Offset>
      <Power> 1.0 0.8 1.5 </Power>
    </SOPNode>
    <SATNode>
      <Saturation> 0.85 </Saturation>
    </SATNode>
  </ColorCorrection>
</ColorCorrectionCollection>

Choose from: Red, Green, Blue, Alpha, Cyan, Magenta, Yellow, Black, Opacity, Index, RGB, RGBA, CMYK, or CMYKA.

The channels above can also be specified as a comma-separated list or can be abbreviated as a concatenation of the letters 'R', 'G', 'B', 'A', 'O', 'C', 'M', 'Y', 'K'. For example, to only select the Red and Blue channels you can either use

-channel Red,Blue

or you can use the short hand form

-channel RB

All the channels that are present in an image can be specified using the special channel type All. Not all operators are 'channel capable', but generally any operators that are generally 'grey-scale' image operators, will understand this setting. See individual operator documentation.

On top of the normal channel selection an extra flag can be specified, 'Sync'. This is turned on by default and if set means that operators that understand this flag should perform: cross-channel synchronization of the channels. If not specified, then most grey-scale operators will apply their image processing operations to each individual channel (as specified by the rest of the -channel setting) completely independently from each other.

For example for operators such as -auto-level and -auto-gamma the color channels are modified together in exactly the same way so that colors will remain in-sync. Without it being set, then each channel is modified separately and independently, which may produce color distortion.

The -morphology 'Convolve' method and the -compose mathematical methods, also understands the 'Sync' flag to modify the behaviour of pixel colors according to the alpha channel (if present). That is to say it will modify the image processing with the understanding that fully-transparent colors should not contribute to the final result.

Basically, by default, operators work with color channels in synchronous, and treats transparency as special, unless the -channel setting is modified so as to remove the effect of the 'Sync' flag. How each operator does this depends on that operators current implementation. Not all operators understands this flag at this time, but that is changing.

To print a complete list of channel types, use -list channel.

By default, ImageMagick sets -channel to the value 'RGBK,sync', which specifies that operators act on all color channels except the transparency channel, and that all the color channels are to be modified in exactly the same way, with an understanding of transparency (depending on the operation being applied). The 'plus' form +channel will reset the value back to this default.

Options that are affected by the -channel setting include the following. -auto-gamma, -auto-level, -black-threshold, -blur, -clamp, -clut, -combine, -composite (Mathematical compose methods only), -convolve, -contrast-stretch, -evaluate, -function, -fx, -gaussian-blur, -hald-clut, -motion-blur, -morphology, -negate, -normalize, -ordered-dither, -radial-blur, -random-threshold, -separate, -threshold, and -white-threshold.

Warning, some operators behave differently when the +channel default setting is in effect, verses ANY user defined -channel setting (including the equivalent of the default). These operators have yet to be made to understand the newer 'Sync' flag.

For example -threshold will by default gray-scale the image before thresholding, if no -channel setting has been defined. This is not 'Sync flag controlled, yet.

Also some operators such as -blur, -gaussian-blur, will modify their handling of the color channels if the 'alpha' channel is also enabled by -channel. Generally this done to ensure that fully-transparent colors are treated as being fully-transparent, and thus any underlying 'hidden' color has no effect on the final results. Typically resulting in 'halo' effects. The newer -morphology convolution equivalents however does have a understanding of the 'Sync' flag and will thus handle transparency correctly by default.

As a alpha channel is optional within images, some operators will read the color channels of an image as a greyscale alpha mask, when the image has no alpha channel present, and the -channel setting tells the operator to apply the operation using alpha channels. The -clut operator is a good example of this.

See Image Geometry for complete details about the geometry argument. The width and height given in the of the size portion of the geometry argument give the number of columns and rows to remove. The offset portion of the geometry argument is influenced by a -gravity setting, if present.

The -chop option removes entire rows and columns, and moves the remaining corner blocks leftward and upward to close the gaps.

While it can remove internal rows and columns of pixels, it is more typically used with as -gravity setting and zero offsets so as to remove a single edge from an image. Compare this to -shave which removes equal numbers of pixels from oppisite sides of the image.

Using -chop effectively undoes the results of a -splice that was given the same geometry and -gravity settings.

If a clipping path is present, it is applied to subsequent operations.

For example, in the command

$ convert -clip -negate cockatoo.tif negated.tif

only the pixels within the clipping path are negated.

The -clip feature requires the XML library. If the XML library is not present, the option is ignored.

Use the given image as a 'do-not-modify' mask of the current images in the current image sequence. Assuming the clipmask is a greyscale image the same size at the one already in memory, any areas that is white will not be modified by any of the 'image processing operators' that follow, until the mask is removed. Pixels in the black areas of the clip mask will be modified as normal.

In some ways this is similar to (though not the same) as defining a rectangular -region, or using the negative of the mask (thrid) image in a three image -composite, operation.

This is almost identical to -clip.

Inside parenthesis (where the operator is normally used) it will make a clone of the images from the last 'pushed' image sequence, and adds them to the end of the current image sequence. Outside parenthesis (not recommended) it clones the images from the current image sequence.

Specify the image by its index in the sequence. The first image is index 0. Negative indexes are relative to the end of the sequence; for example, −1 represents the last image of the sequence. Specify a range of images with a dash (e.g. 0−4). Separate multiple indexes with commas but no spaces (e.g. 0,2,5). A value of '0−−1 will effectively clone all the images.

The +clone will simply make a copy of the last image in the image sequence, and is thus equivalent to using a argument of '−1'.

The second (LUT) image is ordinarily a gradient image containing the histogram mapping of how each channel should be modified. Typically it is a either a single row or column image of replacement color values. If larger than a single row or column, values are taken from a diagonal line from top-left to bottom-right corners.

The lookup is further controlled by the -interpolate setting, which is especially handy for an LUT which is not the full length needed by the ImageMagick installed Quality (Q) level. Good settings for this are the 'bilinear' and 'bicubic' interpolation settings, which give smooth color gradients, and the 'integer' setting for a direct, unsmoothed lookup of color values.

This operator is especially suited to replacing a grayscale image with a specific color gradient from the CLUT image.

Only the channel values defined by the -channel setting will have their values replaced. In particular, since the default -channel setting is RGB, this means that transparency (alpha/matte channel) is not affected, unless the -channel setting is modified. When the alpha channel is set, it is treated by the -clut operator in the same way as the other channels, implying that alpha/matte values are replaced using the alpha/matte values of the original image.

If either the image being modified, or the lookup image, contains no transparency (i.e. -alpha is turned 'off') but the -channel setting includes alpha replacement, then it is assumed that image represents a gray-scale gradient which is used for the replacement alpha values. That is you can use a gray-scale CLUT image to adjust a existing images alpha channel, or you can color a gray-scale image using colors form CLUT containing the desired colors, including transparency.

See also -hald-clut which replaces colors according to the lookup of the full color RGB value from a 2D representation of a 3D color cube.

Overlay each image in an image sequence according to its -dispose meta-data, to reproduce the look of an animation at each point in the animation sequence. All images should be the same size, and are assigned appropriate GIF disposal settings for the animation to continue working as expected as a GIF animation. Such frames are more easily viewed and processed than the highly optimized GIF overlay images.

The animation can be re-optimized after processing using the -layers method 'optimize', although there is no guarantee that the restored GIF animation optimization is better than the original.

Specify the amount of colorization as a percentage. Separate colorization values can be applied to the red, green, and blue channels of the image with a comma-delimited list of colorization values (e.g., -colorize 0,0,50).

The type can be shared or private.

This option only applies when the default X server visual is PseudoColor or GrayScale. Refer to -visual for more details. By default, a shared colormap is allocated. The image shares colors with other X clients. Some image colors could be approximated, therefore your image may look very different than intended. If private is chosen, the image colors appear exactly as they are defined. However, other clients may go technicolor when the image colormap is installed.

The actual number of colors in the image may be less than your request, but never more. Note that this a color reduction option. Images with fewer unique colors than specified by value will have any duplicate or unused colors removed. The ordering of an existing color palette may be altered. When converting an image from color to grayscale, it is more efficient to convert the image to the gray colorspace before reducing the number of colors. Refer to the color reduction algorithm for more details.

This option permits saturation changes, hue rotation, luminance to alpha, and various other effects. Although variable-sized transformation matrices can be used, typically one uses a 5x5 matrix for an RGBA image and a 6x6 for CMYKA (or RGBA with offsets). The matrix is similar to those used by Adobe Flash except offsets are in column 6 rather than 5 (in support of CMYKA images) and offsets are normalized (divide Flash offset by 255).

As an example, to add contrast to an image with offsets, try this command:

   convert kittens.jpg -color-matrix \
     " 1.5 0.0 0.0 0.0, 0.0, -0.157 \
       0.0 1.5 0.0 0.0, 0.0, -0.157 \
       0.0 0.0 1.5 0.0, 0.0, -0.157 \
       0.0 0.0 0.0 1.0, 0.0,  0.0 \
       0.0 0.0 0.0 0.0, 1.0,  0.0 \
       0.0 0.0 0.0 0.0, 0.0,  1.0" kittens.png

Choices are:

   CMY          CMYK         Gray         HSB
   HSL          HWB          Lab          Log
   OHTA         Rec601Luma   Rec601YCbCr  Rec709Luma
   Rec709YCbCr  RGB          sRGB         Transparent
   XYZ          YCbCr        YCC          YIQ
   YPbPr        YUV

To print a complete list of colorspaces, use -list colorspace.

For a more accurate color conversion to or from the RGB, CMYK, or grayscale colorspaces, use the -profile option.

The channels (previously set by -channel) of the combined image are taken from the grayscale values of each image in the sequence, in order. For the default -channel setting of RGB, this means the first image is assigned to the Red channel, the second to the Green channel, the third to the Blue.

This option can be thought of as the inverse to -separate, so long as the channel settings are the same. Thus, in the following example, the final image should be a copy of the original.

$ convert original.png -channel RGB -separate sepimage.png $ convert sepimage-0.png sepimage-1.png sepimage-2.png -channel RGB \
-combine imagecopy.png

This option sets the comment meta-data of an image read in after this option has been given. To modify a comment of images already in memory use "-set comment".

The comment can contain special format characters listed in the Format and Print Image Properties. These attributes are expanded when the comment is finally assigned to the individual images.

If the first character of string is @, the image comment is read from a file titled by the remaining characters in the string. Comments read in from a file are literal; no embedded formatting characters are recognized.

Comment meta-data are not visible on the image itself. To do that use the -annotate or -draw options instead.

For example,

-comment "%m:%f %wx%h" bird.miff

produces an image comment of MIFF:bird.miff 512x480 (assuming that the image bird.miff has a width of 512 and a height of 480.

See Alpha Compositing for a detailed discussion of alpha compositing.

This setting effects image processing operators that merge two (or more) images together in some way. This includes the operators, -composite, -layers composite, -flatten, -mosaic, -layers merge, -border, -frame, and -extent.

It is also one of the primary options for the "composite" command.

Take the first image 'destination' and overlay the second 'source' image according to the current -compose setting. The location of the 'source' or 'overlay' image is controlled according to -geometry, and -geometry settings.

If a third image is given this is treated as a gray-scale 'mask' image relative to the first 'destination' image. This mask will limit what parts of the destination can be modified by the image composition. However for the 'displace' compose method, the mask is used to provide a separate Y-displacement image instead.

If a -compose method requires extra numerical arguments or flags these can be provided by setting the -set 'option:compose:args' appropriately for the compose method.

Some -compose methods can modify the 'destination' image outside the overlay area. You can disable this by setting the special -set 'option:compose:outside-overlay' to 'false'.

Choices are: None, BZip, Fax, Group4, JPEG, JPEG2000, Lossless, LZW, RLE or Zip.

To print a complete list of compression types, use -list compress.

Specify +compress to store the binary image in an uncompressed format. The default is the compression type of the specified image file.

If LZW compression is specified but LZW compression has not been enabled, the image data is written in an uncompressed LZW format that can be read by LZW decoders. This may result in larger-than-expected GIF files.

Lossless refers to lossless JPEG, which is only available if the JPEG library has been patched to support it. Use of lossless JPEG is generally not recommended.

When writing an ICO file, you may request that the images be encoded in PNG format, by specifying Zip compression.

When writing a JNG file, specify Zip compression to request that the alpha channel be encoded in PNG "IDAT" format, or JPEG to request that it be encoded in JPG "JDAA" format.

Use the -quality option to set the compression level to be used by JPEG, PNG, MIFF, and MPEG encoders. Use the -sampling-factor option to set the sampling factor to be used by JPEG, MPEG, and YUV encoders for down-sampling the chroma channels.

This option enhances the intensity differences between the lighter and darker elements of the image. Use -contrast to enhance the image or +contrast to reduce the image contrast.

For a more pronounced effect you can repeat the option:

$ convert rose: -contrast -contrast rose_c2.png

While performing the stretch, black-out at most black-point pixels and white-out at most white-point pixels. Or, if percent is used, black-out at most black-point % pixels and white-out at most white-point % pixels.

Prior to ImageMagick 6.4.7-0, -contrast-stretch will black-out at most black-point pixels and white-out at most total pixels minus white-point pixels. Or, if percent is used, black-out at most black-point % pixels and white-out at most 100% minus white-point % pixels.

Note that -contrast-stretch 0 will modify the image such that the image's min and max values are stretched to 0 and QuantumRange, respectively, without any loss of data due to burn-out or clipping at either end. This is not the same as -normalize, which is equivalent to -contrast-stretch 0.15x0.05% (or prior to ImageMagick 6.4.7-0, -contrast-stretch 2%x99%).

Internally operator works by creating a histogram bin, and then uses that bin to modify the image. As such some colors may be merged together when they originally fell into the same 'bin'.

All the channels are normalized in concert by the came amount so as to preserve color integrity, when the default +channel setting is in use. Specifying any other -channel setting will normalize the RGB channels independently.

See also -auto-level for a 'perfect' normalization of mathematical images.

This operator is under review for re-development.

The kernel is a matrix specified as a comma-separated list of integers (with no spaces), ordered left-to right, starting with the top row. Presently, only odd-dimensioned kernels are supported, and therefore the number of entries in the specified kernel must be 3²=9, 5²=25, 7²=49, etc.

Note that the ‑convolve operator supports the ‑bias setting. This option shifts the convolution so that positive and negative results are relative to a user-specified bias value. This is important for non-HDRI compilations of ImageMagick when dealing with convolutions that contain negative as well as positive values. This is especially the case with convolutions involving high pass filters or edge detection. Without an output bias, the negative values is clipped at zero.

When using an ImageMagick with the HDRI compile-time setting, ‑bias is not needed, as ImageMagick is able to store/handle any negative results without clipping to the color value range (0..QuantumRange). See the discussion on HDRI implementations of ImageMagick on the page High Dynamic-Range Images. For more about HDRI go the ImageMagick Usage pages or this Wikipedia entry.

See Image Geometry for complete details about the geometry argument.

The width and height of the geometry argument give the size of the image that remains after cropping, and x and y in the offset (if present) gives the location of the top left corner of the cropped image with respect to the original image. To specify the amount to be removed, use -shave instead.

If the x and y offsets are present, a single image is generated, consisting of the pixels from the cropping region. The offsets specify the location of the upper left corner of the cropping region measured downward and rightward with respect to the upper left corner of the image. If the -gravity option is present with NorthEast, East, or SouthEast gravity, it gives the distance leftward from the right edge of the image to the right edge of the cropping region. Similarly, if the -gravity option is present with SouthWest, South, or SouthEast gravity, the distance is measured upward between the bottom edges.

If the x and y offsets are omitted, a set of tiles of the specified geometry, covering the entire input image, is generated. The rightmost tiles and the bottom tiles are smaller if the specified geometry extends beyond the dimensions of the input image.

By adding a exclamation character flag to the geometry argument, the cropped images virtual canvas page size and offset is set as if the geometry argument was a viewport or window. This means the canvas page size is set to exactly the same size you specified, the image offset set relative top left corner of the region cropped.

If the cropped image 'missed' the actual image on its virtual canvas, a special single pixel transparent 'missed' image is returned, and a 'crop missed' warning given.

It might be necessary to +repage the image prior to cropping the image to ensure the crop coordinate frame is relocated to the upper-left corner of the visible image. Similarly you may want to use +repage after cropping to remove the page offset that will be left behind. This is especially true when you are going to write to an image format such as PNG that supports an image offset.

Amount defines the number of positions each colormap entry is shifted.

The events parameter specifies which events are to be logged. It can be either None, All, Trace, or a comma-separated list consisting of one or more of the following domains: Accelerate, Annotate, Blob, Cache, Coder, Configure, Deprecate, Exception, Locale, Render, Resource, Security, TemporaryFile, Transform, X11, or User.

For example, to log cache and blob events, use.

$ convert -debug "Cache,Blob" rose: rose.png

The User domain is normally empty, but developers can log user events in their private copy of ImageMagick.

To print the complete list of debug methods, use -list debug.

Use the -log option to specify the format for debugging output.

Use +debug to turn off all logging.

Debugging may also be set using the MAGICK_DEBUG environment variable. The allowed values for the MAGICK_DEBUG environment variable are the same as for the -debug option.

Get the passphrase from the file specified by filename.

For more information, see the webpage, ImageMagick: Encipher or Decipher an Image.

Given a sequence of images all the same size, such as produced by -coalesce, replace the second and later images, with a smaller image of just the area that changed relative to the previous image.

The resulting sequence of images can be used to optimize an animation sequence, though will not work correctly for GIF animations when parts of the animation can go from opaque to transparent.

This option is actually equivalent to the -layers method 'compare-any'.

This option creates one or more definitions for coders and decoders to use while reading and writing image data. Definitions are generally used to control image file format coder modules, and image processing operations, beyond what is provided by normal means. Defined settings are listed in -verbose information ("info:" output format) as "Artifacts".

If value is missing for a definition, an empty-valued definition of a flag is created with that name. This used to control on/off options. Use +define key to remove definitions previously created. Use +define "*" to remove all existing definitions.

The same 'artifact' settings can also be defined using the -set "option:key" "value" option, which also allows the use of Format and Print Image Properties in the defined value.

The option and key are case-independent (they are converted to lowercase for use within the decoders) while the value is case-dependent.

Such settings are global in scope, and effect all images and operations.

The following definitions are just some of the artifacts that are available:

compose:args=arguments

Sets certain compose argument values when using convert ... -compose ... -composite. See Image Composition

distort:scale=value

Sets the output scaling factor for use with -distort

distort:viewport=WxH+X+Y

Sets the viewport for use with -distort

dcm:display-range=reset

Set the display range to the minimum and maximum pixel values for the DCM image format.

dot:layout-engine=value

Set the specify the layout engine for the DOT image format (e.g. neato).

jpeg:extent=value

Restrict the maximum JPEG file size, for example -define jpeg:extent=400kb.

jpeg:size=geometry

Set the size hint of a JPEG image, for example, -define jpeg:size=128x128. It is most useful for increasing performance and reducing the memory requirements when reducing the size of a large JPEG image.

jp2:rate=value

Specify the compression factor to use while writing JPEG-2000 files. The compression factor is the reciprocal of the compression ratio. The valid range is 0.0 to 1.0, with 1.0 indicating lossless compression. If defined, this value overrides the -quality setting. A quality setting of 75 results in a rate value of 0.06641.

mng:need-cacheoff

turn playback caching off for streaming MNG.

png:bit-depth=value

png:color-type=value

desired bit-depth and color-type for PNG output. You can force the PNG encoder to use a different bit-depth and color-type than it would have normally selected, but only if this does not cause any loss of image quality. Any attempt to reduce image quality is treated as an error and no PNG file is written. E.g., if you have a 1-bit black-and-white image, you can use these "defines" to cause it to be written as an 8-bit grayscale, indexed, or even a 64-bit RGBA. But if you have a 16-million color image, you cannot force it to be written as a grayscale or indexed PNG. If you wish to do this, you must use the appropriate -depth, -colors, or -type directives to reduce the image quality prior to using the PNG encoder. Note that in indexed PNG files, "bit-depth" refers to the number of bits per index, which can be 1, 2, 4, or 8. In such files, the color samples always have 8-bit depth.

png:compression-filter=value

valid values are 0 through 7. 0-4 are the corresponding PNG filters, 5 means adaptive filtering except for images with a colormap, 6 means adaptive filtering for all images, 7 means MNG "loco" compression.

png:compression-level=value

valid values are 0 through 9, with 0 providing the least but fastest compression and 9 usually providing the best and always the slowest.

png:compression-strategy=value

valid values are 0 through 4, meaning default, filtered, huffman_only, rle, and fixed ZLIB compression strategy. If you are using an old zlib that does not support Z_RLE (before 1.2.0) or Z_FIXED (before 1.2.2.2), values 3 and 4, respectively, will use the zlib default strategy instead.

png:format=value

valid values are png8, png24, and png32. This property can be useful for specifying the specific PNG format to be used, when the usual method of prepending the format name to the output filename is inconvenient, such as when writing a PNG-encoded ICO file.

png:exclude-chunk=value

png:include-chunk=value

ancillary chunks to be excluded from or included in PNG output.

Thevalue can be the name of a PNG chunk-type such as bKGD, a comma-separated list of chunk-types, or the word all or the word none. There must be no spaces in the list. Although PNG chunk-names are case-dependent, you can use all lowercase names if you prefer.

The "include-chunk" and "exclude-chunk" lists only affect the behavior of the PNG encoder and have no effect on the PNG decoder.

As a special case, if the sRGB chunk is excluded and the gAMA chunk is included, the gAMA chunk will only be written if gamma is not 1/2.2, since most decoders assume sRGB and gamma=1/2.2 when no colorspace information is included in the PNG file. Because the list is processed from left to right, you can achieve this with a single define:

   -define png:include-chunk=none,gAMA

As a special case, if the sRGB chunk is not excluded and the PNG encoder recognizes that the image contains the sRGB ICC profile, the PNG encoder will write the sRGB chunk instead of the entire 3144-byte ICC profile. To force the PNG encoder to write the sRGB profile as an iCCP chunk in the output PNG instead of the sRGB chunk, exclude the sRGB chunk.

The critical PNG chunks IHDR, PLTE, IDAT, and IEND cannot be excluded. Any such entries appearing in the list will be ignored.

If the ancillary PNG tRNS chunk is excluded and the image has transparency, the PNG colortype is forced to be 4 or 6 (GRAY_ALPHA or RGBA). If the image is not transparent, then the tRNS chunk isn't written anyhow, and there is no effect on the PNG colortype of the output image.

The -strip option does the equivalent of the following for PNG output:

   -define png:include-chunk=none,trns,gama

The default behavior is to include all known PNG ancillary chunks plus ImageMagick's private vpAg ("virtual page") chunk, and to exclude all PNG chunks that are unknown to ImageMagick, regardless of their PNG "copy-safe" status as described in the PNG specification.

Any chunk names that are not known to ImageMagick are ignored if they appear in either the "include-chunk" or "exclude-chunk" list. The ancillary chunks currently known to ImageMagick are bKGD, cHRM, gAMA, iCCP, oFFs, pHYs, sRGB, tEXt, tRNS, vpAg, and zTXt.

You can also put date in the list to include or exclude the "Date:create" and "Date:modify" text chunks that ImageMagick normally inserts in the output PNG.

png:preserve-colormap

Use the existing image->colormap. Normally the PNG encoder will try to optimize the palette, eliminating unused entries and putting the transparent colors first. If this flag is set, that behavior is suppressed.

ps:imagemask

If the ps:imagemask flag is defined, the PS3 and EPS3 coders will create Postscript files that render bilevel images with the Postscript imagemask operator instead of the image operator.

quantum:format=type

Set the type to floating-point to specify a floating-point format for raw files (e.g. GRAY:) or for MIFF and TIFF images in HDRI mode to preserve negative values. If -depth 16 is included, the result is a single precision floating point format. If -depth 32 is included, the result is double precision floating point format.

showkernel=1

Outputs (to 'standard error') all the information about a generated -morphology kernel.

tiff:quantum:polarity=min-is-black
tiff:quantum:polarity=min-is-white

Toggles the photometric interpretation

tiff:rows-per-strip=value

Sets the number of rows per strip

tiff:tile-geometry=WxH

Sets the tile size for pyramid tiffs. Requires the suffix PTIF: before the outputname

For example, to create a postscript file that will render only the black pixels of a bilevel image, use:

$ convert bilevel.tif -define ps:imagemask eps3:stencil.ps

Set attributes of the image registry by prefixing the value with registry:. For example, to set a temporary path to put work files, use:

-define registry:temporary-path=/data/tmp

This option is useful for regulating the animation of image sequences ticks/ticks-per-second seconds must expire before the display of the next image. The default is no delay between each showing of the image sequence. The default ticks-per-second is 100.

Use > to change the image delay only if its current value exceeds the given delay. < changes the image delay only if current value is less than the given delay. For example, if you specify 30> and the image delay is 20, the image delay does not change. However, if the image delay is 40 or 50, the delay it is changed to 30. Enclose the given delay in quotation marks to prevent the < or > from being interpreted by your shell as a file redirection.

Specify the image by its index in the sequence. The first image is index 0. Negative indexes are relative to the end of the sequence, for example, -1 represents the last image of the sequence. Specify a range of images with a dash (e.g. 0-4). Separate indexes with a comma (e.g. 0,2). Use +delete to delete the last image in the current image sequence.

This option specifies the image resolution to store while encoding a raster image or the canvas resolution while rendering (reading) vector formats such as Postscript, PDF, WMF, and SVG into a raster image. Image resolution provides the unit of measure to apply when rendering to an output device or raster image. The default unit of measure is in dots per inch (DPI). The -units option may be used to select dots per centimeter instead.

The default resolution is 72 dots per inch, which is equivalent to one point per pixel (Macintosh and Postscript standard). Computer screens are normally 72 or 96 dots per inch, while printers typically support 150, 300, 600, or 1200 dots per inch. To determine the resolution of your display, use a ruler to measure the width of your screen in inches, and divide by the number of horizontal pixels (1024 on a 1024x768 display).

If the file format supports it, this option may be used to update the stored image resolution. Note that Photoshop stores and obtains image resolution from a proprietary embedded profile. If this profile is not stripped from the image, then Photoshop will continue to treat the image using its former resolution, ignoring the image resolution specified in the standard file header.

The -density option sets an attribute and does not alter the underlying raster image. It may be used to adjust the rendered size for desktop publishing purposes by adjusting the scale applied to the pixels. To resize the image so that it is the same size at a different resolution, use the -resample option.

This the number of bits in a color sample within a pixel. Use this option to specify the depth of raw images whose depth is unknown such as GRAY, RGB, or CMYK, or to change the depth of any image after it has been read.

Use -set option:deskew:auto-crop width to auto crop the image. The set argument is the pixel width of the image background (e.g 40).

With this option, the 'overlay' image, and optionally the 'mask' image, is used as a displacement map, which is used to displace the lookup of what part of the 'background' image is seen at each point of the overlaid area. Much like the displacement map is a 'lens' that redirects light shining through it so as to present a distorted view the original 'background' image behind it.

Any perfect grey areas of the displacement map produce a zero displacement of the image. Black areas produce the given maximum negative displacement of the lookup point, while white produce a maximum positive displacement of the lookup.

Note that it is the lookup of the 'background' that is displaced, not a displacement of the image itself. As such an area of the displacement map containing 'white' will have the lookup point 'shifted' by a positive amount, and thus generating a copy of the destination image to the right/downward from the correct position. That is the image will look like it may have been 'shifted' in a negative left/upward direction. Understanding this is a very important in understanding how displacement maps work.

The given arguments define the maximum amount of displacement in pixels that a particular map can produce. If the displacement scale is large enough it is also possible to lookup parts of the 'background' image that lie well outside the bounds of the displacement map itself. That is you could very easily copy a section of the original image from outside the overlay area into the overlay area.

The '%' flag makes the displacement scale relative to the size of the overlay image (100% = half width/height of image). Using '!' switches percentage arguments to refer to the destination image size instead. these flags were added as of IM v6.5.3-5.

Normally a single grayscale displacement map is provided, which with the given scaling values will determine a single direction (vector) in which displacements can occur (positively or negatively). However, if you also specify a third image which is normally used as a mask, the composite image is used for horizontal X displacement, while the mask image is used for vertical Y displacement. This allows you to define completely different displacement values for the X and Y directions, and allowing you to lookup any point within the scale bounds. In other words each pixel can lookup any other nearby pixel, producing complex 2 dimensional displacements, rather than a simple 1 dimensional vector displacements.

Alternatively rather than supplying two separate images, as of IM v6.4.4-0, you can use the 'red' channel of the overlay image to specify the horizontal or X displacement, and the 'green' channel for the vertical or Y displacement.

As of IM v6.5.3-5 any alpha channel in the overlay image is used as a mask the transparency of the destination image. However areas outside the overlaid areas will not be effected.

This option is used with convert for obtaining image or font from this X server. See X(1).

The layer disposal method defines the way each the displayed image is to be modified after the current 'frame' of an animation has finished being displayed (after its 'delay' period), but before the next frame on an animation is to be overlaid onto the display.

Here are the valid methods:

   Undefined   0  No disposal specified (equivalent to 'none').
   None        1  Do not dispose, just overlay next frame image.
   Background  2  Clear the frame area with the background color.
   Previous    3  Clear to the image prior to this frames overlay.

You can also use the numbers given above, which is what the GIF format uses internally to represent the above settings.

To print a complete list of dispose methods, use -list dispose.

Use +dispose, turn off the setting and prevent resetting the layer disposal methods of images being read in.

Use -set 'dispose' method to set the image disposal method for images already in memory.

The opacity of the composite image is multiplied by the given percent, then it is composited 'over' the main image. If src_percent is greater than 100, start dissolving the main image so it becomes transparent at a value of '200'. If both percentages are given, each image are dissolved to the percentages given.

Note that dissolve percentages do not add, two opaque images dissolved '50,50', produce a 75% transparency. For a 50% + 50% blending of the two images, you would need to use dissolve values of '50,100'.

The arguments is a single string containing a list of floating point numbers separated by commas or spaces. The number of and meaning of the floating point values depends on the distortion method being used.

Choose from these distortion types:

To print a complete list of distortion methods, use -list distort.

Many of the above distortion methods such as 'Affine', 'Perspective', and 'Shepards' use a list control points defining how these points in the given image should be distorted in the destination image. Each set of four floating point values represent a source image coordinate, followed immediately by the destination image coordinate. This produces a list of values such as...

where U,V on the source image is mapped to X,Y on the destination image.

For example, to warp an image using 'perspective' distortion, needs a list of at least 4 sets of coordinates, or 16 numbers. Here is the perspective distortion of the built-in "rose:" image. Note how spaces were used to group the 4 sets of coordinate pairs, to make it easier to read and understand.

$ convert rose: -virtual-pixel black \
-distort Perspective '0,0,0,0 0,45,0,45 69,0,60,10 69,45,60,35' \
rose_3d_rotated.gif

If more that the required number of coordinate pairs are given for a distortion, the distortion method is 'least squares' fitted to produce the best result for all the coordinate pairs given. If less than the ideal number of points are given, the distort will generally fall back to a simpler form of distortion that can handles the smaller number of coordinates (usually a linear 'Affine' distortion).

By using more coordinates you can make use of image registration tool to find matching coordinate pairs in overlapping images, so as to improve the 'fit' of the distortion. Of course a bad coordinate pair can also make the 'fit' worse. Caution is always advised.

Colors are acquired from the source image according to the -interpolate color lookup setting, when the image is magnified. However if the viewed image is minified (image becomes smaller), a special area resampling function (added ImageMagick v6.3.5-9), is used to produce a higher quality image. For example you can use a 'perspective' distortion to view a infinitely tiled 'plane' all the way to the horizon.

$ convert -size 90x90 pattern:checkerboard -normalize -virtual-pixel tile \
-distort perspective '0,0,5,45 89,0,45,46 0,89,0,89 89,89,89,89' \
checks_tiled.jpg

Note that a infinitely tiled perspective images involving the horizon can be very slow to generate due to the use of the high quality 'area resampling' function (added ImageMagick v6.3.5-9). You can turn off 'area resampling' using a -filter setting of 'point' (recommended if you plan to use super-sampling instead).

If an image generates invalid pixels, such as the 'sky' in the last 'perspective' distortion example, -distort will use the current -mattecolor setting for these pixels. If you do not what these pixels to be visible, set the color to match the rest of the ground.

The output image size will by default be the same as the input image. This means that if the part of the distorted image falls outside the viewed area of the 'distorted space', those parts is clipped and lost. However if you use the plus form of the operator (+distort) the operator will attempt (if possible) to show the whole of the distorted image, while retaining a correct 'virtual canvas' offset, for image layering. This offset may need to be removed using +repage, to remove if it is unwanted.

You can alternatively specify a special "-set option:distort:viewport {geometry_string}" setting which will specify the size and the offset of the generated 'viewport' image of the distorted image space.

Adding a "-set option:distort:scale {scale_factor}" will scale the output image (viewport or otherwise) by that factor without changing the viewed contents of the distorted image. This can be used either for 'super-sampling' the image for a higher quality result, or for panning and zooming around the image (with appropriate viewport changes, or post-distort cropping and resizing).

Setting -verbose setting, will cause -distort to attempt to output the internal coefficients, and the -fx equivalent to the distortion, for expert study, and debugging purposes. This many not be available for all distorts.

Affine rotations and shears (such as 'SRT' distortion), tend to produce a cleaner result that the equivalent -rotate and/or -shear operation, with more control of due to the above settings. It is algorithmically slower however, though that may not be the case in ImageMagick's implementation.

Dithering places two or more colors in neighboring pixels so that to the eye a closer approximation of the images original color is reproduced. This reduces the number of colors needed to reproduce the image but at the cost of a lower level pattern of colors. Error diffusion dithers can use any set of colors (generated or user defined) to an image.

Dithering is turned on by default, to turn it off use the plus form of the setting, +dither. This will also also render PostScript without text or graphic aliasing. Disabling dithering often (but not always) leads to faster process, a smaller number of colors, but more cartoon like image coloring. Generally resulting in 'color banding' effects in areas with color gradients.

The color reduction operators -colors, -monochrome, -remap, and -posterize, apply dithering to images using the reduced color set they created. These operators are also used as part of automatic color reduction when saving images to formats with limited color support, such as GIF:, XBM:, and others, so dithering may also be used in these cases.

Alternatively you can use -random-threshold to generate purely random dither. Or use -ordered-dither to apply threshold mapped dither patterns, using uniform color maps, rather than specific color maps.

Use this option to annotate or decorate an image with one or more graphic primitives. The primitives include shapes, text, transformations, and pixel operations.

The shape primitives:

   point           x,y
   line            x0,y0 x1,y1
   rectangle       x0,y0 x1,y1
   roundRectangle  x0,y0 x1,y1 wc,hc
   arc             x0,y0 x1,y1 a0,a1
   ellipse         x0,y0 rx,ry a0,a1
   circle          x0,y0 x1,y1
   polyline        x0,y0  ...  xn,yn
   polygon         x0,y0  ...  xn,yn
   bezier          x0,y0  ...  xn,yn
   path            path specification
   image           operator x0,y0 w,h filename

The text primitive:

   text            x0,y0 string

The text gravity primitive:

   gravity         NorthWest, North, NorthEast, West, Center,
                   East, SouthWest, South, or SouthEast

The text gravity primitive only affects the placement of text and does not interact with the other primitives. It is equivalent to using the -gravity command-line option, except that it is limited in scope to the -draw option in which it appears.

The transformation primitives:

   rotate     degrees
   translate  dx,dy
   scale      sx,sy
   skewX      degrees
   skewY      degrees

The pixel operation primitives:

   color  x0,y0 method
   matte  x0,y0 method

The shape primitives are drawn in the color specified by the preceding -fill setting. For unfilled shapes, use -fill none. You can optionally control the stroke (the "outline" of a shape) with the -stroke and -strokewidth settings.

A point primitive is specified by a single point in the pixel plane, that is, by an ordered pair of integer coordinates, x,y. (As it involves only a single pixel, a point primitive is not affected by -stroke or -strokewidth.)

A line primitive requires a start point and end point.

A rectangle primitive is specified by the pair of points at the upper left and lower right corners.

A roundRectangle primitive takes the same corner points as a rectangle followed by the width and height of the rounded corners to be removed.

The circle primitive makes a disk (filled) or circle (unfilled). Give the center and any point on the perimeter (boundary).

The arc primitive is used to inscribe an elliptical segment in to a given rectangle. An arc requires the two corners used for rectangle (see above) followed by the start and end angles of the arc of the segment segment (e.g. 130,30 200,100 45,90). The start and end points produced are then joined with a line segment and the resulting segment of an ellipse is filled.

Use ellipse to draw a partial (or whole) ellipse. Give the center point, the horizontal and vertical "radii" (the semi-axes of the ellipse) and start and end angles in degrees (e.g. 100,100 100,150 0,360).

The polyline and polygon primitives require three or more points to define their perimeters. A polyline is simply a polygon in which the final point is not stroked to the start point. When unfilled, this is a polygonal line. If the -stroke setting is none (the default), then a polyline is identical to a polygon.

A coordinate is a pair of integers separated by a space or optional comma.

As an example, to define a circle centered at 100,100 that extends to 150,150 use:

-draw 'circle 100,100 150,150'

The Bezier primitive creates a spline curve and requires three or points to define its shape. The first and last points are the knots and these points are attained by the curve, while any intermediate coordinates are control points. If two control points are specified, the line between each end knot and its sequentially respective control point determines the tangent direction of the curve at that end. If one control point is specified, the lines from the end knots to the one control point determines the tangent directions of the curve at each end. If more than two control points are specified, then the additional control points act in combination to determine the intermediate shape of the curve. In order to draw complex curves, it is highly recommended either to use the path primitive or to draw multiple four-point bezier segments with the start and end knots of each successive segment repeated. For example:

-draw 'bezier 20,50 45,100 45,0 70,50'

-draw 'bezier 70,50 95,100 95,0 120,50'

A path represents an outline of an object, defined in terms of moveto (set a new current point), lineto (draw a straight line), curveto (draw a Bezier curve), arc (elliptical or circular arc) and closepath (close the current shape by drawing a line to the last moveto) elements. Compound paths (i.e., a path with subpaths, each consisting of a single moveto followed by one or more line or curve operations) are possible to allow effects such as donut holes in objects. (See Paths.)

Use image to composite an image with another image. Follow the image keyword with the composite operator, image location, image size, and filename:

-draw 'image SrcOver 100,100 225,225 image.jpg'

You can use 0,0 for the image size, which means to use the actual dimensions found in the image header. Otherwise, it is scaled to the given dimensions. See Alpha Compositing for a detailed discussion of alpha composition methods that are available.

Use text to annotate an image with text. Follow the text coordinates with a string. If the string has embedded spaces, enclose it in single or double quotes.

For example, the following annotates the image with Works like magick! for an image titled bird.miff.

-draw "text 100,100 'Works like magick!' "

See the -annotate option for another convenient way to annotate an image with text.

The rotate primitive rotates subsequent shape primitives and text primitives about the origin of the main image. If the -region option precedes the -draw option, the origin for transformations is the upper left corner of the region.

The translate primitive translates subsequent shape and text primitives.

The scale primitive scales them.

The skewX and skewY primitives skew them with respect to the origin of the main image or the region.

The transformations modify the current affine matrix, which is initialized from the initial affine matrix defined by the -affine option. Transformations are cumulative within the -draw option. The initial affine matrix is not affected; that matrix is only changed by the appearance of another -affine option. If another -draw option appears, the current affine matrix is reinitialized from the initial affine matrix.

Use the color primitive to change the color of a pixel to the fill color (see -fill). Follow the pixel coordinate with a method:

   point
   replace
   floodfill
   filltoborder
   reset

Consider the target pixel as that specified by your coordinate. The point method recolors the target pixel. The replace method recolors any pixel that matches the color of the target pixel. Floodfill recolors any pixel that matches the color of the target pixel and is a neighbor, whereas filltoborder recolors any neighbor pixel that is not the border color. Finally, reset recolors all pixels.

Use matte to the change the pixel matte value to transparent. Follow the pixel coordinate with a method (see the color primitive for a description of methods). The point method changes the matte value of the target pixel. The replace method changes the matte value of any pixel that matches the color of the target pixel. Floodfill changes the matte value of any pixel that matches the color of the target pixel and is a neighbor, whereas filltoborder changes the matte value of any neighbor pixel that is not the border color (-bordercolor). Finally reset changes the matte value of all pixels.

You can set the primitive color, font, and font bounding box color with -fill, -font, and -box respectively. Options are processed in command line order so be sure to use these options before the -draw option.

Strings that begin with a number must be quoted (e.g. use '1.png' rather than 1.png).

Drawing primitives conform to the Magick Vector Graphics format.

Specify the count and the image to duplicate by its index in the sequence. The first image is index 0. Negative indexes are relative to the end of the sequence, for example, -1 represents the last image of the sequence. Specify a range of images with a dash (e.g. 0-4). Separate indexes with a comma (e.g. 0,2). Use +duplicate to duplicate the last image in the current image sequence.

Get the passphrase from the file specified by filename.

For more information, see the webpage, ImageMagick: Encipher or Decipher an Image.

Choose from AdobeCustom, AdobeExpert, AdobeStandard, AppleRoman, BIG5, GB2312, Latin 2, None, SJIScode, Symbol, Unicode, Wansung.

To print a complete list of endian types, use the -list endian option.

Use +endian to revert to unspecified endianness.

To perform histogram equalization on all channels in concert, transform the image into some other color space, such as HSL, OHTA, YIQ or YUV, then equalize the appropriate intensity-like channel, then convert back to RGB.

For example using HSL, we have: ... -colorspace HSL -channel lightness -equalize -colorspace RGB ...

For YIQ, YUV and OHTA use the red channel. For example, OHTA is a principal components transformation that puts most of the information in the first channel. Here we have ... -colorspace OHTA -channel red -equalize -colorspace RGB ...

(See the -function operator for some multi-parameter functions. See the -fx operator if more elaborate calculations are needed.)

The behaviors of each operator are summarized in the following list. For brevity, the numerical value of a "pixel" referred to below is the value of the corresponding channel of that pixel, while a "normalized pixel" is that number divided by the maximum (installation-dependent) value QuantumRange. (If normalized pixels are used, they are restored, following the other calculations, to the full range by multiplying by QuantumRange.)

The specified functions are applied only to each previously set -channel in the image. If necessary, the results of the calculations are truncated (clipped) to fit in the interval [0, QuantumRange]. The transparency channel of the image is represented as a 'alpha' values (0 = fully transparent), so, for example, a Divide by 2 of the alpha channel will make the image semi-transparent. Append the percent symbol '%' to specify a value as a percentage of the QuantumRange.

To print a complete list of -evaluate operators, use -list evaluate.

The results of the Add, Subtract and Multiply methods can also be achieved using either the -level or the +level operator, with appropriate argument, to linearly modify the overall range of color values. Please note, however, that -level treats transparency as 'matte' values (0 = opaque), while -evaluate works with 'alpha' values.

AddModulus has been added as of ImageMagick 6.4.8-4 and provides addition modulo the QuantumRange. It is therefore equivalent to Add unless the resulting pixel value is outside the interval [0, QuantumRange].

Exp or Exponential has been added as of ImageMagick 6.6.5-1 and works on normalized pixel values. The value used with Exp should be negative so as to produce a decaying exponential function. Non-negative values will always produce results larger unity and thus outside the interval [0, QuantumRange]. The formula is expressed below.

If the input image is squared, for example, using -function polynomial "2 0 0", then a decaying Gaussian function will be the result.

Log has been added as of ImageMagick 6.4.2-1 and works on normalized pixel values. This a scaled log function. The value used with Log provides a scaling factor that adjusts the curvature in the graph of the log function. The formula applied to a normalized value u is below.

Pow has been added as of ImageMagick 6.4.1-9, and works on normalized pixel values. Note that Pow is related to the -gamma operator. For example, -gamma 2 is equivalent to -evaluate pow 0.5, i.e., a 'square root' function. The value used with -gamma is simply the reciprocal of the value used with Pow.

Cosine and Sine was added as of IM v6.4.8-8 and converts the image values into a value according to a (co)sine wave function. The synonyms Cos and Sin may also be used. The output is biased 50% and normalized by 50% so as to fit in the respective color value range. The value scaling of the period of the function (its frequency), and thus determines the number of 'waves' that will be generated over the input color range. For example, if the value is 1, the effective period is simply the QuantumRange; but if the value is 2, then the effective period is the half the QuantumRange.

See also the -function operator, which is a multi-value version of evaluate.

To print a complete list of -evaluate-sequence operators, use -list evaluate.

If the image is enlarged, unfilled areas are set to the background color. To position the image, use offsets in the geometry specification or precede with a -gravity setting. To specify how to compose the image with the background, use -compose.

This command reduces or expands a JPEG image to fit on an 800x600 display. If the aspect ratio of the input image isn't exactly 4:3, then the image is centered on an 800x600 black canvas:

$ convert input.jpg -resize 800x600 -background black -compose Copy \
-gravity center -extent 800x600 -quality 92 output.jpg

See Image Geometry for complete details about the geometry argument.

This option is most useful for extracting a subregion of a very large raw image. Note that these two commands are equivalent:

$ convert -size 16000x16000 -depth 8 -extract 640x480+1280+960 \
image.rgb image.png $ convert -size 16000x16000 -depth 8 'image.rgb[640x480+1280+960]' \
image.rgb image.png

If you omit the offsets, as in

$ convert -size 16000x16000 -depth 8 -extract 640x480 \
image.rgb image.png

the image is resized to the specified dimensions instead, equivalent to:

$ convert -size 16000x16000 -depth 8 -resize 640x480 image.rgb image.png

See Image Geometry for complete details about the geometry argument.

This setting suggests a font family that ImageMagick should try to use for rendering text. If the family can be found it is used; if not, a default font (e.g., "Arial") or a family known to be similar is substituted (e.g., "Courier" might be used if "System" is requested but not found).

For other settings that affect fonts, see the options -font, -stretch, -style, and -weight.

This option is new as of ImageMagick 6.5.4-3 (and now working for Windows users in ImageMagick 6.6.0-9). It transforms an image from the normal (spatial) domain to the frequency domain. In the frequency domain, an image is represented as a superposition of complex sinusoidal waves of varying amplitudes. The image x and y coordinates are the possible frequencies along the x and y directions, respectively, and the pixel intensity values are complex numbers that correspond to the sinusoidal wave amplitudes. See for example, Fourier Transform, Discrete Fourier Transform and Fast Fourier Transform.

A single image name is provided as output for this option. However, the output result will have two components. It is either a two-frame image or two separate images, depending upon whether the image format specified supports multi-frame images. The reason that we get a dual output result is because the frequency domain represents an image using complex numbers, which cannot be visualized directly. Therefore, the complex values are automagically separated into a two-component image representation. The first component is the magnitude of the complex number and the second is the phase of the complex number. See for example, Complex Numbers.

The magnitude and phase component images must be specified using image formats that do not limit the color or compress the image. Thus, MIFF, TIF, PFM, EXR and PNG are the recommended image formats to use. All of these formats, except PNG support multi-frame images. So for example,

$ convert image.png -fft fft_image.miff

generates a magnitude image as fft_image.miff[0] and a phase image as fft_image.miff[1]. Similarly,

$ convert image.png -fft fft_image.png

generates a magnitude image as fft_image-0.png and a phase image as fft_image-1.png. If you prefer this representation, then you can force any of the other formats to produce two output images by including +adjoin following -fft in the command line.

The input image can be any size, but if not square and even-dimensioned, it is padded automagically to the larger of the width or height of the input image and to an even number of pixels. The padding will occur at the bottom and/or right sides of the input image. The resulting output magnitude and phase images is square at this size. The kind of padding relies on the -virtual-pixel setting.

Both output components will have dynamic ranges that fit within [0, QuantumRange], so that HDRI need not be enabled. Phase values nominally range from 0 to 2*π, but is scaled to span the full dynamic range. (The first few releases had non-HDRI scaled but HDRI not scaled). The magnitude image is not scaled and thus generally will contain very small values. As such, the image normally will appear totally black. In order to view any detail, the magnitude image typically is enhanced with a log function into what is usually called the spectrum. A log function is used to enhance the darker values more in comparison to the lighter values. This can be done, for example, as follows:

$ convert fft_image.miff[0] -contrast-stretch 0 \
-evaluate log 1000 fft_image_spectrum.png

where either -contrast-stretch 0 or -auto-level is used to scale the image to full dynamic range, first. The argument to the -evaluate log typically is specified between 100 and 10,000, depending upon the amount of detail that one wants to bring out in the spectrum. Larger values produce more visible detail. Too much detail, however, may hide the important features.

The FFTW delegate library is required to use -fft.

Use +fft to produce two output images that are the real and imaginary components of the complex valued Fourier transform.

However, as the real and imaginary components can contain negative values, this requires that IM be configured with HDRI enabled. In this case, you must use either MIFF, TIF, PFM or MPC formats for the real and imaginary component results, since they are formats that preserve both negative and fractional values without clipping them or truncating the fractional part. With either MIFF or TIF, one should add -define quantum:format=32, to allow those image types to work properly in HDRI mode without clipping.

The real and imaginary component images resulting from +fft are also square, even dimensioned images due to the same padding that was discussed above for the magnitude and phase component images.

See the discussion on HDRI implementations of ImageMagick on the page High Dynamic-Range Images. For more about HDRI go the ImageMagick Usage pages, Fred's Fourier Processing With ImageMagick page or this Wikipedia entry.

This option accepts a color name, a hex color, or a numerical RGB, RGBA, HSL, HSLA, CMYK, or CMYKA specification. See Color Names for a description of how to properly specify the color argument.

Enclose the color specification in quotation marks to prevent the "#" or the parentheses from being interpreted by your shell.

For example,

-fill blue

-fill "#ddddff"

-fill "rgb(255,255,255)"

See -draw for further details.

To print a complete list of color names, use the -list color option.

Use this option to affect the resizing operation of an image during operations such as -resize and -distort. For example you can use a simple resize filter such as:

   Point       Hermite       Cubic
   Box         Gaussian      Catrom
   Triangle    Quadratic     Mitchell

The Bessel and Sinc filter is also provided (as well as a faster SincFast equivalent form). However these filters are generally useless on their own as they are infinite filters that are being clipped to the filters support size. Their direct use is not recommended except via expert settings (see below).

Instead these special filter functions are typically windowed by a windowing function that the -filter setting defines. That is using these functions will define a 'Windowed' filter, appropriate to the operator involved. Windowed filters include:

   Lanczos       Hamming       Parzen
   Blackman      Kaiser        Welsh
   Hanning       Bartlett      Bohman

Also one special self-windowing filter is also provided Lagrange, which will automagically re-adjust its function depending on the current 'support' or 'lobes' expert settings (see below).

If you do not select a filter with this option, the filter defaults to Mitchell for a colormapped image, a image with a matte channel, or if the image is enlarged. Otherwise the filter default to Lanczos.

To print a complete list of resize filters, use the -list filter option.

You can modify how the filter behaves as it scales your image through the use of these expert settings (see also -define and -set):-

-define filter:blur=factor

Scale the X axis of the filter (and its window). Use > 1.0 for blurry or < 1.0 for sharp. This should only be used with Gaussian and Gaussian-like filters simple filters, or you may not get the expected results.

-define filter:support=radius

Set the filter support radius. Defines how large the filter should be and thus directly defines how slow the filtered resampling process is. All filters have a default 'prefered' support size. Some filters like Lagrange and windowed filters adjust themselves depending on this value. With simple filters this value either does nothing (but slow the resampling), or will clip the filter function in a detrimental way.

-define filter:lobes=count

Set the number of lobes to use for the Sinc/Bessel filter. This an alternative way of specifying the 'support' range of the filter, that is designed to be more suited to windowed filters, especially when used for image distorts.

-define filter:sigma=value

The 'sigma' value used to define the Gaussian filter. Default sigma value is '0.5'. It only effects Gaussian but does not shrink (but may enlarge) the filter's 'support'. It can be used to generate very small blurs but without the filter 'missing' pixels due to using a small support setting. A larger value of '0.707' (a value of '1/sqrt(2)') is another common setting.

-define filter:b=b-spline_factor

-define filter:c=keys_alpha_factor

Redefine the values used for cubic filters such as Cubic, Catrom, Mitchel, and Hermite, as well as the Parzen cubic windowing function. If only one of the values are defined, the other is set so as to generate a 'Cubic-Keys' filter. The values meaning was defined by a research paper by Mitchell-Netravali.

-define filter:kaiser-beta=value

The 'alpha' value used to as part of the Kaiser Windowing function. Default value is '6.5'. It only effects Kaiser windowing function, and does not effect any other attributes.

Before IM v6.7.6-10, this option was known as "filter:alpha", (an inheritance from the very old "zoom" program). It was changed to bring the function in line with more modern academic research usage, and better assign it be more definitive.

-define filter:kaiser-alpha=value

This value when multiplied by 'PI' is equivelent to "kaiser-beta", and will override that setting. It only effects Kaiser windowing function, and does not effect any other attributes.

-define filter:filter=filter_function

Use this function directly as the weighting filter. This will allow you to directly use a windowing function such as Blackman, as a resampling filter, rather than as its normal usage as a windowing function.

If defined, no windowing function also defined, the window function is set to Box). Directly specifying Sinc or Jinc as a filter will also do this.

-define filter:window=filter_function

The IIR (infinite impulse response) filters Sinc and Jinc are windowed (brought down to zero over the defined support range) with the given filter. This allows you to specify a filter function to be used as a windowing function for these IIR filters.

Many of the defined filters are actually windowing functions for these IIR filters. A typical choices is Box, (which effectively turns off the windowing function).

-define filter:verbose=1

This causes IM to print information on the final internal filter selection to standard output. This includes a commented header on the filter settings being used, and data allowing the filter weights to be easily graphed.

Note however that some filters are internally defined in terms of other filters. The Lanczos filter for example is defined in terms of a SincFast windowed SincFast filter, while Mitchell is defined as a Cubic filter with specific 'B' and 'C' settings.

For example, to get a 8 lobe Bessel windowed Bessel filter:

$ convert image.png -filter bessel \
-set filter:window=bessel -set filter:lobes=8 \
-resize 150% image.jpg

Or a raw un-windowed Sinc filter with 4 lobes:

$ convert image.png -set filter:filter=sinc -set filter:lobes=4 \
-resize 150% image.jpg

To extract the data for a raw windowing function, combine it with a 'Box' filter. For example the 'Welsh parabolic windowing function.

$ convert null: -define filter:filter=Box \
-define filter:window=Welsh \
-define filter:support=1.0 \
-define filter:verbose=1 \
-resize 2 null: > window_welsh.dat
gnuplot
set grid
plot "window_welsh.dat" with lines

Note that the use of expert options is provided for image processing experts who have studied and understand how resize filters work. Without this knowledge, and an understanding of the definition of the actual filters involved, using expert settings are more likely to be detrimental to your image resizing.

reflect the scanlines in the vertical direction. The image will be mirrored upside-down.

Flood fill starts from the given 'seed point' which is not gravity effected. Any color that matches within -fuzz color distance of the given color argument, connected to that 'seed point' will be replaced with the current -fill color.

Note that if the pixel at the 'seed point' does not itself match the given color (according to -fuzz), then no action will be taken.

This operator works more like the -opaque option, than a more general flood fill that reads the matching color directly at the 'seed point'. For this form of flood fill, look at -draw and its 'color floodfill' drawing method.

Reflect the scanlines in the horizontal direction, just like the image in a vertical mirror.

To print a complete list of fonts, use the -list font option (for versions prior to 6.3.6, use 'type' instead of 'font').

In addition to the fonts specified by the above pre-defined list, you can also specify a font from a specific source. For example Arial.ttf is a TrueType font file, ps:helvetica is PostScript font, and x:fixed is X11 font.

For other settings that affect fonts, see the options -family, -stretch, -style, and -weight.

The color is specified using the format described under the -fill option.

The default foreground color is black.

When used with the mogrify utility, this option converts any image to the image format you specify. For a list of image format types supported by ImageMagick, use -list format.

By default the file is written to its original name. However, if the filename extension matches a supported format, the extension is replaced with the image format type specified with -format. For example, if you specify tiff as the format type and the input image filename is image.gif, the output image filename becomes image.tiff.

See Format and Print Image Properties for an explanation on how to specify the argument to this option.

The color of the border is specified with the -mattecolor command line option.

See Image Geometry for complete details about the geometry argument. The size portion of the geometry argument indicates the amount of extra width and height that is added to the dimensions of the image. If no offsets are given in the geometry argument, then the border added is a solid color. Offsets x and y, if present, specify that the width and height of the border is partitioned to form an outer bevel of thickness x pixels and an inner bevel of thickness y pixels. Negative offsets make no sense as frame arguments.

The -frame option is affected by the current -compose setting and assumes that this is using the default 'Over' composition method. It generates a image of the appropriate size with the current -bordercolor setting, and then draws the frame of four distinct colors close to the current -mattecolor. The original image is then overlaid onto center of this image. This means that with the default compose method of 'Over' any transparent parts may be replaced by the current -bordercolor setting.

The image composition is not affected by the -gravity option.

This operator performs calculations based on the given arguments to modify each of the color values for each previously set -channel in the image. See -evaluate for details concerning how the results of the calculations are handled.

This is can be considered a multi-argument version of the -evaluate operator. (Added in ImageMagick 6.4.8−8.)

Here, parameters is a comma-separated list of numerical values. The number of values varies depending on which function is selected. Choose the function from:

   Polynomial
   Sinusoid
   Arcsin
   Arctan

To print a complete list of -function operators, use -list function. Descriptions follow.

Polynomial

The Polynomial function takes an arbitrary number of parameters, these being the coefficients of a polynomial, in decreasing order of degree. That is, entering

-function Polynomial a_n,a_n-1,...a₁,a₀

will invoke a polynomial function given by

a_n uⁿ + a_n-1 u^n-1 + ··· a₁ u + a₀,

where u is pixel's original normalized channel value.

The Polynomial function can be used in place of Set (the constant polynomial) and Add, Divide, Multiply, and Subtract (some linear polynomials) of the -evaluate operator. The -level operator also affects channels linearly. Some correspondences follow.

-evaluate Set value	-function Polynomial value	(Constant functions; set value×100% gray when channels are RGB.)
-evaluate Add value	-function Polynomial 1,value
-evaluate Subtract value	-function Polynomial 1,−value
-evaluate Multiply value	-function Polynomial value,0
+level black% x white%	-function Polynomial A,B	(Reduce contrast. Here, A=(white-black)/100 and B=black/100.)

The Polynomial function gives great versatility, since polynomials can be used to fit any continuous curve to any degree of accuracy desired.

Sinusoid

The Sinusoid function can be used to vary the channel values sinusoidally by setting frequency, phase shift, amplitude, and a bias. These values are given as one to four parameters, as follows,

-function Sinusoid freq,[phase,[amp,[bias]]]

where phase is in degrees. (The domain [0,1] of the function corresponds to 0 through freq×360 degrees.) The result is that if a pixel's normalized channel value is originally u, its resulting normalized value is given by

amp * sin(2*π* (freq * u + phase / 360)) + bias

For example, the following generates a curve that starts and ends at 0.9 (when u=0 and 1, resp.), oscillating three times between .7−.2=.5 and .7+.2=.9.

-function Sinusoid 3,-90,.2,.7

The default values of amp and bias are both .5. The default for phase is 0.

The Sinusoid function generalizes Sin and Cos of the -evaluate operator by allowing varying amplitude, phase and bias. The correspondence is as follows.

-evaluate Sin freq	-function Sinusoid freq,0
-evaluate Cos freq	-function Sinusoid freq,90

ArcSin

The ArcSin function generates the inverse curve of a Sinusoid, and can be used to generate cylindrical distortion and displacement maps. The curve can be adjusted relative to both the input values and output range of values.

-function ArcSin width,[center,[range,[bias]]]

with all values given in terms of normalized color values (0.0 for black, 1.0 for white). Defaulting to values covering the full range from 0.0 to 1.0 for bout input (width), and output (width) values. '1.0,0.5,1.0,0.5'

range/π * asin( 2/width * ( u - center ) ) + bias

ArcTan

The ArcTan function generates a curve that smooth crosses from limit values at infinities, though a center using the given slope value. All these values can be adjusted via the arguments.

-function ArcTan slope,[center,[range,[bias]]]

Defaulting to '1.0,0.5,1.0,0.5'.

range/π * atan( slope*π * ( u - center ) ) + bias

A number of algorithms search for a target color. By default the color must be exact. Use this option to match colors that are close to the target color in RGB space. For example, if you want to automagically trim the edges of an image with -trim but the image was scanned and the target background color may differ by a small amount. This option can account for these differences.

The distance can be in absolute intensity units or, by appending % as a percentage of the maximum possible intensity (255, 65535, or 4294967295).

If the first character of expression is @, the expression is read from a file titled by the remaining characters in the string.

See FX, The Special Effects Image Operator for a detailed discussion of this option.

The same color image displayed on two different workstations may look different due to differences in the display monitor. Use gamma correction to adjust for this color difference. Reasonable values extend from 0.8 to 2.3. Gamma less than 1.0 darkens the image and gamma greater than 1.0 lightens it. Large adjustments to image gamma may result in the loss of some image information if the pixel quantum size is only eight bits (quantum range 0 to 255).

Gamma adjusts the image's channel values pixel-by-pixel according to a power law, namely, pow(pixel,1/gamma) or pixel^(1/gamma), where pixel is the normalized or 0 to 1 color value. For example, using a value of gamma=2 is the same as taking the square root of the image.

You can apply separate gamma values to the red, green, and blue channels of the image with a gamma value list delimited with commas (e.g., 1.7,2.3,1.2).

Use +gamma value to set the image gamma level without actually adjusting the image pixels. This option is useful if the image is of a known gamma but not set as an image attribute (e.g. PNG images). Write the "file gamma" which is the reciprocal of the display gamma; e.g., if your image is sRGB and you want to write a PNG gAMA chunk, use

$ convert input.png +gamma .45455 output.png

Note that gamma adjustments are also available via the -level operator.

Convolve the image with a Gaussian or normal distribution using the given Sigma value. The formula is:

The Sigma value is the important argument, and determines the actual amount of blurring that will take place.

The Radius is only used to determine the size of the array which will hold the calculated Gaussian distribution. It should be an integer. If not given, or set to zero, IM will calculate the largest possible radius that will provide meaningful results for the Gaussian distribution.

The larger the Radius the radius the slower the operation is. However too small a Radius, and sever aliasing effects may result. As a guideline, Radius should be at least twice the Sigma value, though three times will produce a more accurate result.

This differs from the faster -blur operator in that a full 2-dimensional convolution is used to generate the weighted average of the neighboring pixels.

The -virtual-pixel setting will determine how pixels which are outside the image proper are blurred into the final result.

See Image Geometry for complete details about the geometry argument.

Choices include: NorthWest, North, NorthEast, West, Center, East, SouthWest, South, SouthEast. Use -list gravity to get a complete list of -gravity settings available in your ImageMagick installation.

The direction you choose specifies where to position text or subimages. For example, a gravity of Center forces the text to be centered within the image. By default, the image gravity is NorthWest. See -draw for more details about graphic primitives. Only the text primitive of -draw is affected by the -gravity option.

The -gravity option is also used in concert with the -geometry setting and other settings or options that take geometry as an argument, such as the -crop option.

If a -gravity setting occurs before another option or setting having a geometry argument that specifies an offset, the offset is usually applied to the point within the image suggested by the -gravity argument. Thus, in the following command, for example, suppose the file image.png has dimensions 200x100. The offset specified by the argument to -region is (−40,+20). The argument to -gravity is Center, which suggests the midpoint of the image, at the point (100,50). The offset (−40,20) is applied to that point, giving (100−40,50+20)=(60,70), so the specified 10x10 region is located at that point. (In addition, the -gravity affects the region itself, which is centered at the pixel coordinate (60,70). (See Image Geometry for complete details about the geometry argument.)

$ convert image.png -gravity Center -region 10x10-40+20 \
-negate output.png

When used as an option to composite, -gravity gives the direction that the image gravitates within the composite.

When used as an option to montage, -gravity gives the direction that an image gravitates within a tile. The default gravity is Center for this purpose.

A Hald color lookup table is a 3-dimensional color cube mapped to 2 dimensions. Create it with the HALD: prefix (e.g. HALD:8). You can apply any color transformation to the Hald image and then use this option to apply the transform to the image.

$ convert image.png hald.png -hald-clut transform.png

This option provides a convenient method for you to use Gimp or Photoshop to make color corrections to the Hald CLUT image and subsequently apply them to multiple images using an ImageMagick script.

Note that the representation is only of the normal RGB color space and that the whole color value triplet is used for the interpolated lookup of the represented Hald color cube image. Because of this the operation is not -channel setting effected, nor can it adjust or modify an images transparency or alpha/matte channel.

See also -clut which provides color value replacement of the individual color channels, usually involving a simpler gray-scale image. E.g: gray-scale to color replacement, or modification by a histogram mapping.

Offsets, if present in the geometry specification, are handled in the same manner as the -geometry option, using X11 style to handle negative offsets.

See Image Geometry for complete details about the geometry argument.

This information is printed: image scene number; image name; image size; the image class (DirectClass or PseudoClass); the total number of unique colors; and the number of seconds to read and transform the image. Refer to MIFF for a description of the image class.

If -colors is also specified, the total unique colors in the image and color reduction error values are printed. Refer to color reduction algorithm for a description of these values.

If -verbose precedes this option, copious amounts of image properties are displayed including image statistics, profiles, image histogram, and others.

This option is new as of ImageMagick 6.5.4-3 (and now working for Windows users in ImageMagick 6.6.0-9). It transforms a pair of magnitude and phase images from the frequency domain to a single image in the normal or spatial domain. See for example, Fourier Transform, Discrete Fourier Transform and Fast Fourier Transform.

For example, depending upon the image format used to store the result of the -fft, one would use either

$ convert fft_image.miff -ift fft_image_ift.png

or

$ convert fft_image-0.png fft_image-1.png -ift fft_image_ift.png

The resulting image may need to be cropped due to padding introduced when the original image, prior to the -fft or +fft, was not square or even dimensioned. Any padding is at the right and/or bottom sides of the image.

The FFTW delegate library is required to use -ift.

Use +ift (with HDRI enabled) to transform a pair of real and imaginary images from the frequency domain to a single image in the normal (spatial) domain.

This option takes last image in the current image sequence and inserts it at the given index. If a negative index is used, the insert position is calculated before the last image is removed from the sequence. As such -insert -1 will result in no change to the image sequence.

The +insert option is equivalent to -insert -1. In other words, insert the last image, at the end of the current image sequence. Consequently this has no effect on the image sequence order.

Use this option to affect the color management operation of an image (see -profile). Choose from these intents: Absolute, Perceptual, Relative, Saturation.

The default intent is Perceptual for the sRGB colorspace and undefined for the RGB and gray colorspaces.

To print a complete list of rendering intents, use -list intent.

Choose from:

   none
   line
   plane
   partition
   JPEG
   GIF
   PNG

This option is used to specify the type of interlacing scheme for raw image formats such as RGB or YUV.

None means do not interlace (RGBRGBRGBRGBRGBRGB...),

Line uses scanline interlacing (RRR...GGG...BBB...RRR...GGG...BBB...), and.

Plane uses plane interlacing (RRRRRR...GGGGGG...BBBBBB...).

Partition is like plane except the different planes are saved to individual files (e.g. image.R, image.G, and image.B).

Use Line or Plane to create an interlaced PNG or GIF or progressive JPEG image.

To print a complete list of interlacing schemes, use -list interlace.

When looking up the color of a pixel using a non-integer floating point value, you typically fall in between the pixel colors defined by the source image. This setting determines how the color is determined from the colors of the pixels surrounding that point. That is how to determine the color of a point that falls between two, or even four different colored pixels.

   integer           The color of the top-left pixel (floor function)
   nearest-neighbor  The nearest pixel to the lookup point (rounded function)
   average           The average color of the surrounding four pixels
   bilinear          A double linear interpolation of pixels (the default)
   mesh              Divide area into two flat triangular interpolations
   bicubic           Fitted bicubic-spines of surrounding 16 pixels
   spline            Direct spline curves (colors are blurred)
   filter            Use resize -filter settings

This most important for distortion operators such as -distort, -implode, -transform and -fx.

To print a complete list of interpolation methods, use -list interpolate.

See also -virtual-pixel, for control of the lookup for positions outside the boundaries of the image.

Use this option to assign a specific label to the image, as it is read in or created. You can use the -set operation to re-assign a the labels of images already read in. Image formats such as TIFF, PNG, MIFF, supports saving the label information with the image.

When saving an image to a PostScript file, any label assigned to an image is used as a header string to print above the postscript image.

You can include the image filename, type, width, height, or other image attribute by embedding special format character. See Format and Print Image Properties for details of the percent escape codes.

For example,

-label "%m:%f %wx%h" bird.miff

assigns an image label of MIFF:bird.miff 512x480 to the "bird.miff" image and whose width is 512 and height is 480, as it is read in. If a +label option was used instead, any existing label present in the image would be used. You can remove all labels from an image by assigning the empty string.

A label is not drawn on the image, but is embedded in the image datastream via Label tag or similar mechanism. If you want the label to be visible on the image itself, use the -draw option, or during the final processing in the creation of a image montage.

If the first character of string is @, the image label is read from a file titled by the remaining characters in the string. Labels in a file are literal, no embedded formatting characters are recognized.

Adaptively threshold each pixel based on the value of pixels in a surrounding window. If the current pixel is lighter than this average plus the optional offset, then it is made white, otherwise it is made black. Small variations in pixel values such as found in scanned documents can be ignored if offset is positive. A negative offset will make it more sensitive to those small variations.

This is commonly used to threshold images with an uneven background. It is based on the assumption that average color of the small window is the the local background color, from which to separate the foreground color.

Perform various image operation methods to a ordered sequence of images which may represent either a set of overlaid 'image layers', a GIF disposal animation, or a fully-'coalesced' animation sequence.

To print a complete list of layer types, use -list layers.

The operators -coalesce, -deconstruct, -flatten, and -mosaic are only aliases for the above methods and may be depreciated in the future. Also see -page, -repage operators, the -compose setting, and the GIF -dispose and -delay settings.

Given one, two or three values delimited with commas: black-point, white-point, gamma (for example: 10,250,1.0 or 2%,98%,0.5). The black and white points range from 0 to QuantumRange, or from 0 to 100%; if the white point is omitted it is set to (QuantumRange - black_point), so as to center contrast changes. If a % sign is present anywhere in the string, both black and white points are percentages of the full color range. Gamma will do a -gamma adjustment of the values. If it is omitted, the default of 1.0 (no gamma correction) is assumed.

In normal usage (-level) the image values are stretched so that the given 'black_point' value in the original image is set to zero (or black), while the given 'white_point' value is set to QuantumRange (or white). This provides you with direct contrast adjustments to the image. The 'gamma' of the resulting image will then be adjusted.

From ImageMagick v6.4.1-9 using the plus form of the operator (+level) or adding the special '!' flag anywhere in the argument list, will cause the operator to do the reverse of the level adjustment. That is a zero, or QuantumRange value (black, and white, resp.) in the original image, is adjusted to the given level values, allowing you to de-contrast, or compress the channel values within the image. The 'gamma' is adjusted before the level adjustment to de-contrast the image is made.

Only the channels defined by the current -channel setting are adjusted (defaults to RGB color channels only), allowing you to limit the effect of this operator.

Please note that the transparency channel is treated as 'matte' values (0 is opaque) and not as 'alpha' values (0 is transparent).

This function is exactly like -level, except that the value value for each color channel is determined by the 'black_color' and 'white_color' colors given (as described under the -fill option).

This effectually means the colors provided to -level-colors is mapped to become 'black' and 'white' respectively, with all the other colors linearly adjusted (or clipped) to match that change. Each channel is adjusted separately using the channel values of the colors specified.

On the other hand the plus form of the operator (+level-colors) will map the image color 'black' and 'white' to the given colors respectively, resulting in a gradient (de-contrasting) tint of the image to those colors. This can also be used to convert a plain gray-scale image into a one using the gradient of colors specified.

By supplying a single color with a comma separator either before or after that color, will just replace the respective 'black' or 'white' point respectively. But if no comma separator is provided, the given color is used for both the black and white color points, making the operator either threshold the images around that color (- form) or set all colors to that color (+ form).

Choose from: area, disk, file, map, memory, threads, or time.

The value for file is in number of files. The other limits are in bytes. Define arguments for the memory, map, area, and disk resource limits with SI prefixes (.e.g 100MB).

By default the limits are 768 files, 2GB of image area, 1.5GiB memory, 8GiB memory map, and 18.45EB of disk. These limits are adjusted relative to the available resources on your computer if this information is available. When any limit is reached, ImageMagick fails in some fashion but attempts to take compensating actions, if possible. For example, the following limits memory:

-limit memory 32MiB -limit map 64MiB

Use -list resource to list the current limits. For example, our system shows these limits:

$ identify -list resource

  File         Area       Memory          Map         Disk   Thread         Time
  ------------------------------------------------------------------------------
   768     12.404GB    8.6642GiB    23.104GiB  18.446744EB        8    unlimited

Requests for pixel storage to keep intermediate images are satisfied by one of three resource categories: in-memory pool, memory-mapped files pool, and disk pool (in that order) depending on the ‑limit settings and whether the system honors a resource request. If the total size of allocated pixel storage in the given pool reaches the corresponding limit, the request is passed to the next pool. Additionally, requests that exceed the area limit automagically are allocated on disk.

To illustrate how ImageMagick utilizes resource limits, consider a typical image resource request. First, ImageMagick tries to allocate the pixels in memory. The request might be denied if the resource request exceeds the memory limit or if the system does not honor the request. If a memory request is not honored, the pixels are allocated to disk and the file is memory-mapped. However, if the allocation request exceeds the map limit, the resource allocation goes to disk. In all cases, if the resource request exceeds the area limit, the pixels are automagically cached to disk. If the disk has a hard limit, the program fails.

In most cases you simply do not need to concern yourself with resource limits. ImageMagick chooses reasonable defaults and most images do not tax your computer resources. Where limits do come in handy is when you process images that are large or on shared systems where ImageMagick can consume all or most of the available memory. In this case, the ImageMagick workflow slows other processes or, in extreme cases, brings the system to a halt. Under these circumstances, setting limits give some assurances that the ImageMagick workflow will not interfere with other concurrent uses of the computer. For example, assume you have a web interface that processes images uploaded from the Internet. To assure ImageMagick does not exceed 10mb of memory you can simply set the area limit to 10mb:

-limit area 10mb

Now whenever a large image is processed, the pixels are automagically cached to disk instead of memory. This of course implies that large images typically process very slowly, simply because pixel processing in memory can be an order of magnitude faster than on disk. Because your web site users might inadvertently upload a huge image to process, you should set a disk limit as well:

-limit area 10mb -limit disk 500mb

Here ImageMagick stops processing if an image requires more than 500MB of disk storage.

In addition to command-line resource limit option, resources can be set with environment variables. Set the environment variables MAGICK_AREA_LIMIT, MAGICK_DISK_LIMIT, MAGICK_FILE_LIMIT, MAGICK_MEMORY_LIMIT, MAGICK_MAP_LIMIT, MAGICK_THREAD_LIMIT, MAGICK_TIME_LIMIT for limits of image area, disk space, open files, heap memory, memory map, number of threads of execution, and maximum elapsed time in seconds respectively.

Inquisitive users can try adding -debug cache to their commands and then scouring the generated output for references to the pixel cache, in order to determine how the pixel cache was allocated and how resources were consumed. Advanced Unix/Linux users can pipe that output through grep memory|open|destroy|disk for more readable sifting.

For more about ImageMagick's use of resources, see the section Cache Storage and Resource Requirements on the Architecture page.

This is very similar to -contrast-stretch, and uses a 'histogram bin' to determine the range of color values that needs to be stretched. However it then stretches those colors using the -level operator.

As such while the initial determination may have 'binning' round off effects, the image colors are stretched mathematically, rather than using the histogram bins. This makes the operator more accurate.

note however that a -linear-stretch of '0' does nothing, while a value of '1' does a near perfect stretch of the color range.

See also -auto-level for a 'perfect' normalization of mathematical images.

This operator is under review for re-development.

See Image Geometry for complete details about the geometry argument.

   Align          Alpha          Boolean        Channel
   Class          ClipPath       Coder          Color
   Colorspace     Command        Compose        Compress
   Configure      DataType       Debug          Decoration
   Delegate       Direction      Dispose        Distort
   Dither         Endian         Evaluate       FillRule
   Filter         Font           Format         Function
   Gravity        ImageList      Intent         Interlace
   Interpolate    Kernel         Layers         LineCap
   LineJoin       List           Locale         LogEvent
   Log            Magic          Method         Metric
   Mime           Mode           Morphology     Module
   Noise          Orientation    Policy         PolicyDomain
   PolicyRights   Preview        Primitive      QuantumFormat
   Resource       SparseColor    Storage        Stretch
   Style          Threshold      Type           Units
   Validate       VirtualPixel

These lists vary depending on your version of ImageMagick. Use "-list list" to get a complete listing of all the "-list" arguments available:

$ identify -list list

This option specifies the format for the log printed when the -debug option is active.

You can display the following components by embedding special format characters:

   %d  domain
   %e  event
   %f  function
   %l  line
   %m  module
   %p  process ID
   %r  real CPU time
   %t  wall clock time
   %u  user CPU time
   %%  percent sign
   \n  newline
   \r  carriage return

For example:

$ convert -debug coders -log "%u %m:%l %e" in.gif out.png

The default behavior is to print all of the components.

Set iterations to zero to repeat the animation an infinite number of times, otherwise the animation repeats itself up to iterations times.

Choose from these Standard Colormap types:

   best
   default
   gray
   red
   green
   blue

The X server must support the Standard Colormap you choose, otherwise an error occurs. Use list as the type and display searches the list of colormap types in top-to-bottom order until one is located. See xstdcmap(1) for one way of creating Standard Colormaps.

Here are the valid components of a map:

   r  red pixel component
   g  green pixel component
   b  blue pixel component
   a  alpha pixel component (0 is transparent)
   o  opacity pixel component (0 is opaque)
   i  grayscale intensity pixel component
   c  cyan pixel component
   m  magenta pixel component
   y  yellow pixel component
   k  black pixel component
   p  pad component (always 0)

You can specify as many of these components as needed in any order (e.g. bgr). The components can repeat as well (e.g. rgbr).

This the same as using a mask used for composite masking operations, with grayscale values causing blended updates of the image the mask is attached to.

Use +mask to remove the mask from images.

Also see -clip-mask which work in the same way, but with strict boolean masking.

The color is specified using the format described under the -fill option.

The default matte color is #BDBDBD, this shade of gray.

Select the 'maximum' value from all the surrounding pixels.

This is legacy option from the method of the same name.

Select the 'middle' value from all the surrounding pixels.

This is legacy option from the method of the same name.

Choose from:

  AE     absolute error count, number of different pixels (-fuzz effected)
  FUZZ   mean color distance
  MAE    mean absolute error (normalized), average channel error distance
  MEPP   mean error per pixel (normalized mean error, normalized peak error)
  MSE    mean error squared, average of the channel error squared
  NCC    normalized cross correlation
  PAE    peak absolute (normalize peak absolute)
  PSNR   peak signal to noise ratio
  RMSE   root mean squared (normalized root mean squared)

Control the 'AE', or absolute count of pixels that are different, with the -fuzz factor (ignore pixels which only changed by a small amount). Use 'PAE' to find the size of the -fuzz factor needed to make all pixels 'similar', while 'MAE' determines the factor needed for about half the pixels to be similar.

The 'MEPP' metric returns three different metrics ('MAE', 'MAE' normalized, and 'PAE' normalized) from a single comparison run.

To print a complete list of metrics, use the -list metrics option.

Select the 'minimal' value from all the surrounding pixels.

This is legacy option from the method of the same name.

Choose the value from these styles: Frame, Unframe, or Concatenate

Use the -list option with a 'Mode' argument for a list of -mode arguments available in your ImageMagick installation.

The arguments are given as a percentages of variation. A value of 100 means no change, and any missing values are taken to mean 100.

The brightness is a multiplier of the overall brightness of the image, so 0 means pure black, 50 is half as bright, 200 is twice as bright. To invert its meaning -negate the image before and after.

The saturation controls the amount of color in an image. For example, 0 produce a grayscale image, while a large value such as 200 produce a very colorful, 'cartoonish' color.

The hue argument causes a "rotation" of the colors within the image by the amount specified. For example, 50 results in a counter-clockwise rotation of 90, mapping red shades to purple, and so on. A value of either 0 or 200 results in a complete 180 degree rotation of the image. Using a value of 300 is a 360 degree rotation resulting in no change to the original image.

For example, to increase the color brightness by 20% and decrease the color saturation by 10% and leave the hue unchanged, use -modulate 120,90.

Use -set attribute of 'option:modulate:colorspace' to specify which colorspace to modulate. Choose from HSB, HSL (the default), or HWB. For example,

$ convert image.png -set option:modulate:colorspace hsb -modulate 120,90 modulate.png

Both the image pixels and size are linearly interpolated to give the appearance of a metamorphosis from one image to the next, over all the images in the current image list. The added images are the equivalent of a -blend composition. The frames argument determine how many images to interpolate between each image.

Until I get around to writing an option summary for this, see IM Usage Examples, Morphology.

Blur with the given radius, standard deviation (sigma), and angle. The angle given is the angle toward which the image is blurred. That is the direction people would consider the object is coming from.

Note that the blur is not uniform distribution, giving the motion a definite sense of direction of movement.

The -virtual-pixel setting will determine how pixels which are outside the image proper are blurred into the final result.

The red, green, and blue intensities of an image are negated. White becomes black, yellow becomes blue, etc. Use +negate to only negate the grayscale pixels of the image.

The principal function of noise peak elimination filter is to smooth the objects within an image without losing edge information and without creating undesired structures. The central idea of the algorithm is to replace a pixel with its next neighbor in value within a pixel window, if this pixel has been found to be noise. A pixel is defined as noise if and only if this pixel is a maximum or minimum within the pixel window.

Use -noise radius to specify the width of the neighborhood when reducing noise. This is equivelent to using a -statistic NonPeak operation, which should be used in preference.

Use +noise followed by a noise type to add noise to an image. Choose from these noise types:

   Gaussian
   Impulse
   Laplacian
   Multiplicative
   Poisson
   Random
   Uniform

The amount of noise added can be controled by the -attenuate setting. If unset the value is equivelent to 1.0, or a maximum noise addition.

To print a complete list of noises, use the -list noise option.

Also see the -evaluate noise functions that allows the use of a controlling value to specify the amount of noise that should be added to an image.

The intensity values are stretched to cover the entire range of possible values. While doing so, black-out at most 2% of the pixels and white-out at most 1% of the pixels.

Note that as of ImageMagick 6.4.7-0, -normalize is equivalent to -contrast-stretch 2%x1%. (Before this version, it was equivalent to -contrast-stretch 2%x99%).

All the channels are normalized in concert by the came amount so as to preserve color integrity, when the default +channel setting is in use. Specifying any other -channel setting will normalize the RGB channels independently.

See -contrast-stretch for more details. Also see -auto-level for a 'perfect' normalization that is better suited to mathematically generated images.

This operator is under review for re-development.

You can choose from these standard threshold maps:

   threshold   1x1   Threshold 1x1 (non-dither)
   checks      2x1   Checkerboard 2x1 (dither)
   o2x2        2x2   Ordered 2x2 (dispersed)
   o3x3        3x3   Ordered 3x3 (dispersed)
   o4x4        4x4   Ordered 4x4 (dispersed)
   o8x8        8x8   Ordered 8x8 (dispersed)
   h4x4a       4x1   Halftone 4x4 (angled)
   h6x6a       6x1   Halftone 6x6 (angled)
   h8x8a       8x1   Halftone 8x8 (angled)
   h4x4o             Halftone 4x4 (orthogonal)
   h6x6o             Halftone 6x6 (orthogonal)
   h8x8o             Halftone 8x8 (orthogonal)
   h16x16o           Halftone 16x16 (orthogonal)
   c5x5b       c5x5  Circles 5x5 (black)
   c5x5w             Circles 5x5 (white)
   c6x6b       c6x6  Circles 6x6 (black)
   c6x6w             Circles 6x6 (white)
   c7x7b       c7x7  Circles 7x7 (black)
   c7x7w             Circles 7x7 (white)

The threshold generated a simple 50% threshold of the image. This could be used with level to do the equivalent of -posterize to reduce an image to basic primary colors.

The checks pattern produces a 3 level checkerboard dither pattern. That is a grayscale will become a pattern of solid black, solid white, and mid-tone colors into a checkerboard pattern of black and white.

You can define your own threshold map for ordered dithering and halftoning your images, in either personal or system thresholds.xml XML file. See Resources for more details of configuration files.

To print a complete list of the thresholds that have been defined, use the -list threshold option.

Note that at this time the same threshold dithering map is used for all color channels, no attempt is made to offset or rotate the map for different channels is made, to create an offset printing effect. Also as the maps are simple threshold levels, the halftone and circle maps will create incomplete circles along the edges of a colored area. Also all the effects are purely on/off boolean effects, without anti-aliasing to make the circles smooth looking. Large dots can be made to look better with a small amount of blurring after being created.

The color argument is defined using the format described under the -fill option. The -fuzz setting can be used to match and replace colors similar to the one given.

Use +opaque to paint any pixel that does not match the target color.

The -transparent operator is exactly the same as -opaque but replaces the matching color with transparency rather than the current -fill color setting. To ensure that it can do this it also ensures that the image has an alpha channel enabled, as per "-alpha set", for the new transparent colors, and does not require you to modify the -channel to enable alpha channel handling.

Choose from these orientations:

   bottom-left
   bottom-right
   left-bottom
   left-top
   right-bottom
   right-top
   top-left
   top-right
   undefined

To print a complete list of orientations, use the -list orientation option.

See Image Geometry for complete details about the geometry argument.

For convenience you can specify the page size using media (see below). Offsets can then be added as with other geometry arguments (e.g. -page Letter+43+43).

Use media as shorthand to specify the dimensions (widthxheight) of the PostScript page in dots per inch or a TEXT page in pixels. The choices for a PostScript page are:

This option is also used to place subimages when writing to a multi-image format that supports offsets, such as GIF89 and MNG. When used for this purpose the offsets are always measured from the top left corner of the canvas and are not affected by the -gravity option. To position a GIF or MNG image, use -page{+-}x{+-}y (e.g. -page +100+200). When writing to a MNG file, a -page option appearing ahead of the first image in the sequence with nonzero width and height defines the width and height values that are written in the MHDR chunk. Otherwise, the MNG width and height are computed from the bounding box that contains all images in the sequence. When writing a GIF89 file, only the bounding box method is used to determine its dimensions.

For a PostScript page, the image is sized as in -geometry but positioned relative to the lower left-hand corner of the page by {+-}xoffset{+-}y offset. Use -page 612x792, for example, to center the image within the page. If the image size exceeds the PostScript page, it is reduced to fit the page. The default gravity for the -page option is NorthWest, i.e., positive x and y offset are measured rightward and downward from the top left corner of the page, unless the -gravity option is present with a value other than NorthWest.

The default page dimensions for a TEXT image is 612x792.

This option is used in concert with -density.

Use +page to remove the page settings for an image.

Each pixel is replaced by the most frequent color in a circular neighborhood whose width is specified with radius.

Pause for the specified number of seconds before repeating the animation.

Pause for the specified number of seconds before taking the next snapshot.

Use +polaroid to rotate the image at a random angle between -15 and +15 degrees.

Use this option to affect the preview operation of an image (e.g. convert file.png -preview Gamma Preview:gamma.png). Choose from these previews:

   Rotate           Shear            Roll             Hue
   Saturation       Brightness       Gamma            Spiff
   Dull             Grayscale        Quantize         Despeckle
   ReduceNoise      Add Noise        Sharpen          Blur
   Threshold        EdgeDetect       Spread           Shade
   Raise            Segment          Solarize         Swirl
   Implode          Wave             OilPaint         CharcoalDrawing
   JPEG

To print a complete list of previews, use the -list m> specified, and a uniform color map with the given number of levels per color channel .

You can choose from these standard threshold maps:

   threshold   1x1   Threshold 1x1 (non-dither)
   checks      2x1   Checkerboard 2x1 (dither)
   o2x2        2x2   Ordered 2x2 (dispersed)
   o3x3        3x3   Ordered 3x3 (dispersed)
   o4x4        4x4   Ordered 4x4 (dispersed)
   o8x8        8x8   Ordered 8x8 (dispersed)
   h4x4a       4x1   Halftone 4x4 (angled)
   h6x6a       6x1   Halftone 6x6 (angled)
   h8x8a       8x1   Halftone 8x8 (angled)
   h4x4o             Halftone 4x4 (orthogonal)
   h6x6o             Halftone 6x6 (orthogonal)
   h8x8o             Halftone 8x8 (orthogonal)
   h16x16o           Halftone 16x16 (orthogonal)
   c5x5b       c5x5  Circles 5x5 (black)
   c5x5w             Circles 5x5 (white)
   c6x6b       c6x6  Circles 6x6 (black)
   c6x6w             Circles 6x6 (white)
   c7x7b       c7x7  Circles 7x7 (black)
   c7x7w             Circles 7x7 (white)

The threshold generated a simple 50% threshold of the image. This could be used with level to do the equivalent of -posterize to reduce an image to basic primary colors.

The checks pattern produces a 3 level checkerboard dither pattern. That is a grayscale will become a pattern of solid black, solid white, and mid-tone colors into a checkerboard pattern of black and white.

You can define your own threshold map for ordered dithering and halftoning your images, in either personal or system thresholds.xml XML file. See Resources for more details of configuration files.

To print a complete list of the thresholds that have been defined, use the -list threshold option.

Note that at this time the same threshold dithering map is used for all color channels, no attempt is made to offset or rotate the map for different channels is made, to create an offset printing effect. Also as the maps are simple threshold levels, the halftone and circle maps will create incomplete circles along the edges of a colored area. Also all the effects are purely on/off boolean effects, without anti-aliasing to make the circles smooth looking. Large dots can be made to look better with a small amount of blurring after being created.

The color argument is defined using the format described under the -fill option. The -fuzz setting can be used to match and replace colors similar to the one given.

Use +opaque to paint any pixel that does not match the target color.

The -transparent operator is exactly the same as -opaque but replaces the matching color with transparency rather than the current -fill color setting. To ensure that it can do this it also ensures that the image has an alpha channel enabled, as per "-alpha set", for the new transparent colors, and does not require you to modify the -channel to enable alpha channel handling.

Choose from these orientations:

   bottom-left
   bottom-right
   left-bottom
   left-top
   right-bottom
   right-top
   top-left
   top-right
   undefined

To print a complete list of orientations, use the -list orientation option.

See Image Geometry for complete details about the geometry argument.

For convenience you can specify the page size using media (see below). Offsets can then be added as with other geometry arguments (e.g. -page Letter+43+43).

Use media as shorthand to specify the dimensions (widthxheight) of the PostScript page in dots per inch or a TEXT page in pixels. The choices for a PostScript page are:

This option is also used to place subimages when writing to a multi-image format that supports offsets, such as GIF89 and MNG. When used for this purpose the offsets are always measured from the top left corner of the canvas and are not affected by the -gravity option. To position a GIF or MNG image, use -page{+-}x{+-}y (e.g. -page +100+200). When writing to a MNG file, a -page option appearing ahead of the first image in the sequence with nonzero width and height defines the width and height values that are written in the MHDR chunk. Otherwise, the MNG width and height are computed from the bounding box that contains all images in the sequence. When writing a GIF89 file, only the bounding box method is used to determine its dimensions.

For a PostScript page, the image is sized as in -geometry but positioned relative to the lower left-hand corner of the page by {+-}xoffset{+-}y offset. Use -page 612x792, for example, to center the image within the page. If the image size exceeds the PostScript page, it is reduced to fit the page. The default gravity for the -page option is NorthWest, i.e., positive x and y offset are measured rightward and downward from the top left corner of the page, unless the -gravity option is present with a value other than NorthWest.

The default page dimensions for a TEXT image is 612x792.

This option is used in concert with -density.

Use +page to remove the page settings for an image.

Each pixel is replaced by the most frequent color in a circular neighborhood whose width is specified with radius.

Pause for the specified number of seconds before repeating the animation.

Pause for the specified number of seconds before taking the next snapshot.

Use +polaroid to rotate the image at a random angle between -15 and +15 degrees.

Use this option to affect the preview operation of an image (e.g. convert file.png -preview Gamma Preview:gamma.png). Choose from these previews:

   Rotate           Shear            Roll             Hue
   Saturation       Brightness       Gamma            Spiff
   Dull             Grayscale        Quantize         Despeckle
   ReduceNoise      Add Noise        Sharpen          Blur
   Threshold        EdgeDetect       Spread           Shade
   Raise            Segment          Solarize         Swirl
   Implode          Wave             OilPaint         CharcoalDrawing
   JPEG

To print a complete list of previews, use the -list m> specified, and a uniform color map with the given number of levels per color channel .

You can choose from these standard threshold maps:

   threshold   1x1   Threshold 1x1 (non-dither)
   checks      2x1   Checkerboard 2x1 (dither)
   o2x2        2x2   Ordered 2x2 (dispersed)
   o3x3        3x3   Ordered 3x3 (dispersed)
   o4x4        4x4   Ordered 4x4 (dispersed)
   o8x8        8x8   Ordered 8x8 (dispersed)
   h4x4a       4x1   Halftone 4x4 (angled)
   h6x6a       6x1   Halftone 6x6 (angled)
   h8x8a       8x1   Halftone 8x8 (angled)
   h4x4o             Halftone 4x4 (orthogonal)
   h6x6o             Halftone 6x6 (orthogonal)
   h8x8o             Halftone 8x8 (orthogonal)
   h16x16o           Halftone 16x16 (orthogonal)
   c5x5b       c5x5  Circles 5x5 (black)
   c5x5w             Circles 5x5 (white)
   c6x6b       c6x6  Circles 6x6 (black)
   c6x6w             Circles 6x6 (white)
   c7x7b       c7x7  Circles 7x7 (black)
   c7x7w             Circles 7x7 (white)

The threshold generated a simple 50% threshold of the image. This could be used with level to do the equivalent of -posterize to reduce an image to basic primary colors.

The checks pattern produces a 3 level checkerboard dither pattern. That is a grayscale will become a pattern of solid black, solid white, and mid-tone colors into a checkerboard pattern of black and white.

You can define your own threshold map for ordered dithering and halftoning your images, in either personal or system thresholds.xml XML file. See Resources for more details of configuration files.

To print a complete list of the thresholds that have been defined, use the -list threshold option.

Note that at this time the same threshold dithering map is used for all color channels, no attempt is made to offset or rotate the map for different channels is made, to create an offset printing effect. Also as the maps are simple threshold levels, the halftone and circle maps will create incomplete circles along the edges of a colored area. Also all the effects are purely on/off boolean effects, without anti-aliasing to make the circles smooth looking. Large dots can be made to look better with a small amount of blurring after being created.

The color argument is defined using the format described under the -fill option. The -fuzz setting can be used to match and replace colors similar to the one given.

Use +opaque to paint any pixel that does not match the target color.

The -transparent operator is exactly the same as -opaque but replaces the matching color with transparency rather than the current -fill color setting. To ensure that it can do this it also ensures that the image has an alpha channel enabled, as per "-alpha set", for the new transparent colors, and does not require you to modify the -channel to enable alpha channel handling.

Choose from these orientations:

   bottom-left
   bottom-right
   left-bottom
   left-top
   right-bottom
   right-top
   top-left
   top-right
   undefined

To print a complete list of orientations, use the -list orientation option.

See Image Geometry for complete details about the geometry argument.

For convenience you can specify the page size using media (see below). Offsets can then be added as with other geometry arguments (e.g. -page Letter+43+43).

Use media as shorthand to specify the dimensions (widthxheight) of the PostScript page in dots per inch or a TEXT page in pixels. The choices for a PostScript page are:

This option is also used to place subimages when writing to a multi-image format that supports offsets, such as GIF89 and MNG. When used for this purpose the offsets are always measured from the top left corner of the canvas and are not affected by the -gravity option. To position a GIF or MNG image, use -page{+-}x{+-}y (e.g. -page +100+200). When writing to a MNG file, a -page option appearing ahead of the first image in the sequence with nonzero width and height defines the width and height values that are written in the MHDR chunk. Otherwise, the MNG width and height are computed from the bounding box that contains all images in the sequence. When writing a GIF89 file, only the bounding box method is used to determine its dimensions.

For a PostScript page, the image is sized as in -geometry but positioned relative to the lower left-hand corner of the page by {+-}xoffset{+-}y offset. Use -page 612x792, for example, to center the image within the page. If the image size exceeds the PostScript page, it is reduced to fit the page. The default gravity for the -page option is NorthWest, i.e., positive x and y offset are measured rightward and downward from the top left corner of the page, unless the -gravity option is present with a value other than NorthWest.

The default page dimensions for a TEXT image is 612x792.

This option is used in concert with -density.

Use +page to remove the page settings for an image.

Each pixel is replaced by the most frequent color in a circular neighborhood whose width is specified with radius.

Pause for the specified number of seconds before repeating the animation.

Pause for the specified number of seconds before taking the next snapshot.

Use +polaroid to rotate the image at a random angle between -15 and +15 degrees.

Use this option to affect the preview operation of an image (e.g. convert file.png -preview Gamma Preview:gamma.png). Choose from these previews:

   Rotate           Shear            Roll             Hue
   Saturation       Brightness       Gamma            Spiff
   Dull             Grayscale        Quantize         Despeckle
   ReduceNoise      Add Noise        Sharpen          Blur
   Threshold        EdgeDetect       Spread           Shade
   Raise            Segment          Solarize         Swirl
   Implode          Wave             OilPaint         CharcoalDrawing
   JPEG

To print a complete list of previews, use the -list m> specified, and a uniform color map with the given number of levels per color channel .

You can choose from these standard threshold maps:

   threshold   1x1   Threshold 1x1 (non-dither)
   checks      2x1   Checkerboard 2x1 (dither)
   o2x2        2x2   Ordered 2x2 (dispersed)
   o3x3        3x3   Ordered 3x3 (dispersed)
   o4x4        4x4   Ordered 4x4 (dispersed)
   o8x8        8x8   Ordered 8x8 (dispersed)
   h4x4a       4x1   Halftone 4x4 (angled)
   h6x6a       6x1   Halftone 6x6 (angled)
   h8x8a       8x1   Halftone 8x8 (angled)
   h4x4o             Halftone 4x4 (orthogonal)
   h6x6o             Halftone 6x6 (orthogonal)
   h8x8o             Halftone 8x8 (orthogonal)
   h16x16o           Halftone 16x16 (orthogonal)
   c5x5b       c5x5  Circles 5x5 (black)
   c5x5w             Circles 5x5 (white)
   c6x6b       c6x6  Circles 6x6 (black)
   c6x6w             Circles 6x6 (white)
   c7x7b       c7x7  Circles 7x7 (black)
   c7x7w             Circles 7x7 (white)

The threshold generated a simple 50% threshold of the image. This could be used with level to do the equivalent of -posterize to reduce an image to basic primary colors.

The checks pattern produces a 3 level checkerboard dither pattern. That is a grayscale will become a pattern of solid black, solid white, and mid-tone colors into a checkerboard pattern of black and white.

You can define your own threshold map for ordered dithering and halftoning your images, in either personal or system thresholds.xml XML file. See Resources for more details of configuration files.

To print a complete list of the thresholds that have been defined, use the -list threshold option.

Note that at this time the same threshold dithering map is used for all color channels, no attempt is made to offset or rotate the map for different channels is made, to create an offset printing effect. Also as the maps are simple threshold levels, the halftone and circle maps will create incomplete circles along the edges of a colored area. Also all the effects are purely on/off boolean effects, without anti-aliasing to make the circles smooth looking. Large dots can be made to look better with a small amount of blurring after being created.

The color argument is defined using the format described under the -fill option. The -fuzz setting can be used to match and replace colors similar to the one given.

Use +opaque to paint any pixel that does not match the target color.

The -transparent operator is exactly the same as -opaque but replaces the matching color with transparency rather than the current -fill color setting. To ensure that it can do this it also ensures that the image has an alpha channel enabled, as per "-alpha set", for the new transparent colors, and does not require you to modify the -channel to enable alpha channel handling.

Choose from these orientations:

   bottom-left
   bottom-right
   left-bottom
   left-top
   right-bottom
   right-top
   top-left
   top-right
   undefined

To print a complete list of orientations, use the -list orientation option.

See Image Geometry for complete details about the geometry argument.

For convenience you can specify the page size using media (see below). Offsets can then be added as with other geometry arguments (e.g. -page Letter+43+43).

Use media as shorthand to specify the dimensions (widthxheight) of the PostScript page in dots per inch or a TEXT page in pixels. The choices for a PostScript page are:

This option is also used to place subimages when writing to a multi-image format that supports offsets, such as GIF89 and MNG. When used for this purpose the offsets are always measured from the top left corner of the canvas and are not affected by the -gravity option. To position a GIF or MNG image, use -page{+-}x{+-}y (e.g. -page +100+200). When writing to a MNG file, a -page option appearing ahead of the first image in the sequence with nonzero width and height defines the width and height values that are written in the MHDR chunk. Otherwise, the MNG width and height are computed from the bounding box that contains all images in the sequence. When writing a GIF89 file, only the bounding box method is used to determine its dimensions.

For a PostScript page, the image is sized as in -geometry but positioned relative to the lower left-hand corner of the page by {+-}xoffset{+-}y offset. Use -page 612x792, for example, to center the image within the page. If the image size exceeds the PostScript page, it is reduced to fit the page. The default gravity for the -page option is NorthWest, i.e., positive x and y offset are measured rightward and downward from the top left corner of the page, unless the -gravity option is present with a value other than NorthWest.

The default page dimensions for a TEXT image is 612x792.

This option is used in concert with -density.

Use +page to remove the page settings for an image.

Each pixel is replaced by the most frequent color in a circular neighborhood whose width is specified with radius.

Pause for the specified number of seconds before repeating the animation.

Pause for the specified number of seconds before taking the next snapshot.

Use +polaroid to rotate the image at a random angle between -15 and +15 degrees.

Use this option to affect the preview operation of an image (e.g. convert file.png -preview Gamma Preview:gamma.png). Choose from these previews:

   Rotate           Shear            Roll             Hue
   Saturation       Brightness       Gamma            Spiff
   Dull             Grayscale        Quantize         Despeckle
   ReduceNoise      Add Noise        Sharpen          Blur
   Threshold        EdgeDetect       Spread           Shade
   Raise            Segment          Solarize         Swirl
   Implode          Wave             OilPaint         CharcoalDrawing
   JPEG

To print a complete list of previews, use the -list m> specified, and a uniform color map with the given number of levels per color channel .

You can choose from these standard threshold maps:

   threshold   1x1   Threshold 1x1 (non-dither)
   checks      2x1   Checkerboard 2x1 (dither)
   o2x2        2x2   Ordered 2x2 (dispersed)
   o3x3        3x3   Ordered 3x3 (dispersed)
   o4x4        4x4   Ordered 4x4 (dispersed)
   o8x8        8x8   Ordered 8x8 (dispersed)
   h4x4a       4x1   Halftone 4x4 (angled)
   h6x6a       6x1   Halftone 6x6 (angled)
   h8x8a       8x1   Halftone 8x8 (angled)
   h4x4o             Halftone 4x4 (orthogonal)
   h6x6o             Halftone 6x6 (orthogonal)
   h8x8o             Halftone 8x8 (orthogonal)
   h16x16o           Halftone 16x16 (orthogonal)
   c5x5b       c5x5  Circles 5x5 (black)
   c5x5w             Circles 5x5 (white)
   c6x6b       c6x6  Circles 6x6 (black)
   c6x6w             Circles 6x6 (white)
   c7x7b       c7x7  Circles 7x7 (black)
   c7x7w             Circles 7x7 (white)

The threshold generated a simple 50% threshold of the image. This could be used with level to do the equivalent of -posterize to reduce an image to basic primary colors.

The checks pattern produces a 3 level checkerboard dither pattern. That is a grayscale will become a pattern of solid black, solid white, and mid-tone colors into a checkerboard pattern of black and white.

You can define your own threshold map for ordered dithering and halftoning your images, in either personal or system thresholds.xml XML file. See Resources for more details of configuration files.

To print a complete list of the thresholds that have been defined, use the -list threshold option.

Note that at this time the same threshold dithering map is used for all color channels, no attempt is made to offset or rotate the map for different channels is made, to create an offset printing effect. Also as the maps are simple threshold levels, the halftone and circle maps will create incomplete circles along the edges of a colored area. Also all the effects are purely on/off boolean effects, without anti-aliasing to make the circles smooth looking. Large dots can be made to look better with a small amount of blurring after being created.

The color argument is defined using the format described under the -fill option. The -fuzz setting can be used to match and replace colors similar to the one given.

Use +opaque to paint any pixel that does not match the target color.

The -transparent operator is exactly the same as -opaque but replaces the matching color with transparency rather than the current -fill color setting. To ensure that it can do this it also ensures that the image has an alpha channel enabled, as per "-alpha set", for the new transparent colors, and does not require you to modify the -channel to enable alpha channel handling.

Choose from these orientations:

   bottom-left
   bottom-right
   left-bottom
   left-top
   right-bottom
   right-top
   top-left
   top-right
   undefined

To print a complete list of orientations, use the -list orientation option.

See Image Geometry for complete details about the geometry argument.

For convenience you can specify the page size using media (see below). Offsets can then be added as with other geometry arguments (e.g. -page Letter+43+43).

Use media as shorthand to specify the dimensions (widthxheight) of the PostScript page in dots per inch or a TEXT page in pixels. The choices for a PostScript page are:

This option is also used to place subimages when writing to a multi-image format that supports offsets, such as GIF89 and MNG. When used for this purpose the offsets are always measured from the top left corner of the canvas and are not affected by the -gravity option. To position a GIF or MNG image, use -page{+-}x{+-}y (e.g. -page +100+200). When writing to a MNG file, a -page option appearing ahead of the first image in the sequence with nonzero width and height defines the width and height values that are written in the MHDR chunk. Otherwise, the MNG width and height are computed from the bounding box that contains all images in the sequence. When writing a GIF89 file, only the bounding box method is used to determine its dimensions.

For a PostScript page, the image is sized as in -geometry but positioned relative to the lower left-hand corner of the page by {+-}xoffset{+-}y offset. Use -page 612x792, for example, to center the image within the page. If the image size exceeds the PostScript page, it is reduced to fit the page. The default gravity for the -page option is NorthWest, i.e., positive x and y offset are measured rightward and downward from the top left corner of the page, unless the -gravity option is present with a value other than NorthWest.

The default page dimensions for a TEXT image is 612x792.

This option is used in concert with -density.

Use +page to remove the page settings for an image.

Each pixel is replaced by the most frequent color in a circular neighborhood whose width is specified with radius.

Pause for the specified number of seconds before repeating the animation.

Pause for the specified number of seconds before taking the next snapshot.

Use +polaroid to rotate the image at a random angle between -15 and +15 degrees.

Use this option to affect the preview operation of an image (e.g. convert file.png -preview Gamma Preview:gamma.png). Choose from these previews:

   Rotate           Shear            Roll             Hue
   Saturation       Brightness       Gamma            Spiff
   Dull             Grayscale        Quantize         Despeckle
   ReduceNoise      Add Noise        Sharpen          Blur
   Threshold        EdgeDetect       Spread           Shade
   Raise            Segment          Solarize         Swirl
   Implode          Wave             OilPaint         CharcoalDrawing
   JPEG

To print a complete list of previews, use the -list m> specified, and a uniform color map with the given number of levels per color channel .

You can choose from these standard threshold maps:

   threshold   1x1   Threshold 1x1 (non-dither)
   checks      2x1   Checkerboard 2x1 (dither)
   o2x2        2x2   Ordered 2x2 (dispersed)
   o3x3        3x3   Ordered 3x3 (dispersed)
   o4x4        4x4   Ordered 4x4 (dispersed)
   o8x8        8x8   Ordered 8x8 (dispersed)
   h4x4a       4x1   Halftone 4x4 (angled)
   h6x6a       6x1   Halftone 6x6 (angled)
   h8x8a       8x1   Halftone 8x8 (angled)
   h4x4o             Halftone 4x4 (orthogonal)
   h6x6o             Halftone 6x6 (orthogonal)
   h8x8o             Halftone 8x8 (orthogonal)
   h16x16o           Halftone 16x16 (orthogonal)
   c5x5b       c5x5  Circles 5x5 (black)
   c5x5w             Circles 5x5 (white)
   c6x6b       c6x6  Circles 6x6 (black)
   c6x6w             Circles 6x6 (white)
   c7x7b       c7x7  Circles 7x7 (black)
   c7x7w             Circles 7x7 (white)

The threshold generated a simple 50% threshold of the image. This could be used with level to do the equivalent of -posterize to reduce an image to basic primary colors.

The checks pattern produces a 3 level checkerboard dither pattern. That is a grayscale will become a pattern of solid black, solid white, and mid-tone colors into a checkerboard pattern of black and white.

You can define your own threshold map for ordered dithering and halftoning your images, in either personal or system thresholds.xml XML file. See Resources for more details of configuration files.

To print a complete list of the thresholds that have been defined, use the -list threshold option.

Note that at this time the same threshold dithering map is used for all color channels, no attempt is made to offset or rotate the map for different channels is made, to create an offset printing effect. Also as the maps are simple threshold levels, the halftone and circle maps will create incomplete circles along the edges of a colored area. Also all the effects are purely on/off boolean effects, without anti-aliasing to make the circles smooth looking. Large dots can be made to look better with a small amount of blurring after being created.

The color argument is defined using the format described under the -fill option. The -fuzz setting can be used to match and replace colors similar to the one given.

Use +opaque to paint any pixel that does not match the target color.

The -transparent operator is exactly the same as -opaque but replaces the matching color with transparency rather than the current -fill color setting. To ensure that it can do this it also ensures that the image has an alpha channel enabled, as per "-alpha set", for the new transparent colors, and does not require you to modify the -channel to enable alpha channel handling.

Choose from these orientations:

   bottom-left
   bottom-right
   left-bottom
   left-top
   right-bottom
   right-top
   top-left
   top-right
   undefined

To print a complete list of orientations, use the -list orientation option.

See Image Geometry for complete details about the geometry argument.

For convenience you can specify the page size using media (see below). Offsets can then be added as with other geometry arguments (e.g. -page Letter+43+43).

Use media as shorthand to specify the dimensions (widthxheight) of the PostScript page in dots per inch or a TEXT page in pixels. The choices for a PostScript page are:

This option is also used to place subimages when writing to a multi-image format that supports offsets, such as GIF89 and MNG. When used for this purpose the offsets are always measured from the top left corner of the canvas and are not affected by the -gravity option. To position a GIF or MNG image, use -page{+-}x{+-}y (e.g. -page +100+200). When writing to a MNG file, a -page option appearing ahead of the first image in the sequence with nonzero width and height defines the width and height values that are written in the MHDR chunk. Otherwise, the MNG width and height are computed from the bounding box that contains all images in the sequence. When writing a GIF89 file, only the bounding box method is used to determine its dimensions.

For a PostScript page, the image is sized as in -geometry but positioned relative to the lower left-hand corner of the page by {+-}xoffset{+-}y offset. Use -page 612x792, for example, to center the image within the page. If the image size exceeds the PostScript page, it is reduced to fit the page. The default gravity for the -page option is NorthWest, i.e., positive x and y offset are measured rightward and downward from the top left corner of the page, unless the -gravity option is present with a value other than NorthWest.

The default page dimensions for a TEXT image is 612x792.

This option is used in concert with -density.

Use +page to remove the page settings for an image.

Each pixel is replaced by the most frequent color in a circular neighborhood whose width is specified with radius.

Pause for the specified number of seconds before repeating the animation.

Pause for the specified number of seconds before taking the next snapshot.

Use +polaroid to rotate the image at a random angle between -15 and +15 degrees.

Use this option to affect the preview operation of an image (e.g. convert file.png -preview Gamma Preview:gamma.png). Choose from these previews:

   Rotate           Shear            Roll             Hue
   Saturation       Brightness       Gamma            Spiff
   Dull             Grayscale        Quantize         Despeckle
   ReduceNoise      Add Noise        Sharpen          Blur
   Threshold        EdgeDetect       Spread           Shade
   Raise            Segment          Solarize         Swirl
   Implode          Wave             OilPaint         CharcoalDrawing
   JPEG

To print a complete list of previews, use the -list m> specified, and a uniform color map with the given number of levels per color channel .

You can choose from these standard threshold maps:

   threshold   1x1   Threshold 1x1 (non-dither)
   checks      2x1   Checkerboard 2x1 (dither)
   o2x2        2x2   Ordered 2x2 (dispersed)
   o3x3        3x3   Ordered 3x3 (dispersed)
   o4x4        4x4   Ordered 4x4 (dispersed)
   o8x8        8x8   Ordered 8x8 (dispersed)
   h4x4a       4x1   Halftone 4x4 (angled)
   h6x6a       6x1   Halftone 6x6 (angled)
   h8x8a       8x1   Halftone 8x8 (angled)
   h4x4o             Halftone 4x4 (orthogonal)
   h6x6o             Halftone 6x6 (orthogonal)
   h8x8o             Halftone 8x8 (orthogonal)
   h16x16o           Halftone 16x16 (orthogonal)
   c5x5b       c5x5  Circles 5x5 (black)
   c5x5w             Circles 5x5 (white)
   c6x6b       c6x6  Circles 6x6 (black)
   c6x6w             Circles 6x6 (white)
   c7x7b       c7x7  Circles 7x7 (black)
   c7x7w             Circles 7x7 (white)

The threshold generated a simple 50% threshold of the image. This could be used with level to do the equivalent of -posterize to reduce an image to basic primary colors.

The checks pattern produces a 3 level checkerboard dither pattern. That is a grayscale will become a pattern of solid black, solid white, and mid-tone colors into a checkerboard pattern of black and white.

You can define your own threshold map for ordered dithering and halftoning your images, in either personal or system thresholds.xml XML file. See Resources for more details of configuration files.

To print a complete list of the thresholds that have been defined, use the -list threshold option.

Note that at this time the same threshold dithering map is used for all color channels, no attempt is made to offset or rotate the map for different channels is made, to create an offset printing effect. Also as the maps are simple threshold levels, the halftone and circle maps will create incomplete circles along the edges of a colored area. Also all the effects are purely on/off boolean effects, without anti-aliasing to make the circles smooth looking. Large dots can be made to look better with a small amount of blurring after being created.

The color argument is defined using the format described under the -fill option. The -fuzz setting can be used to match and replace colors similar to the one given.

Use +opaque to paint any pixel that does not match the target color.

The -transparent operator is exactly the same as -opaque but replaces the matching color with transparency rather than the current -fill color setting. To ensure that it can do this it also ensures that the image has an alpha channel enabled, as per "-alpha set", for the new transparent colors, and does not require you to modify the -channel to enable alpha channel handling.

Choose from these orientations:

   bottom-left
   bottom-right
   left-bottom
   left-top
   right-bottom
   right-top
   top-left
   top-right
   undefined

To print a complete list of orientations, use the -list orientation option.

See Image Geometry for complete details about the geometry argument.

For convenience you can specify the page size using media (see below). Offsets can then be added as with other geometry arguments (e.g. -page Letter+43+43).

Use media as shorthand to specify the dimensions (widthxheight) of the PostScript page in dots per inch or a TEXT page in pixels. The choices for a PostScript page are: