From glennrp@ARL.MIL  Sat Jul 27 04:43:17 1996
Date:     Sat, 27 Jul 96 8:43:17 EDT
From: Glenn Randers-Pehrson ARL-WMRD-TED-TIB <glennrp@ARL.MIL>
To: iana@isi.edu
Cc: boutell@boutell.com
Subject:  Registration of new Media Type image/png
Content-Length: 2047
Status: RO
X-Lines: 50



To:  IANA@isi.edu
Subject:  Registration of new Media Type image/png

Media Type name: image

Media subtype name: png

Required parameters: None

Optional parameters: None

Encoding considerations: base64 generally preferred

Security considerations:
  A PNG document is composed of a collection of explicitly typed "chunks".
  For each of the chunk types defined in the PNG specification (except
  for "gIFx"), the only effect associated with those chunks is to cause
  an image to be rendered on the recipient's display or printer.

  The gIFx chunk type is used to encapsulate Application Extension
  data, and some use of that data might present security risks, though
  no risks are known.  Likewise, the security risks associated with
  future chunk types cannot be evaluated, particularly unregistered
  chunks.  However, it is the intention of the PNG group to disallow
  chunks containing "executable" data to become registered chunks.

  The text chunks, tEXt and zTXt, contain data that can be displayed in
  the form of comments, etc.  Some operating systems or terminals might
  allow the display of textual data with embedded control characters to
  perform operations such as re-mapping of keys, creation of files, etc.
  For this reason, the specification recommends that the text chunks be
  filtered for control characters before direct display.

  The PNG format is specifically designed to facilitate early detection
  of file transmission errors, and makes use of cyclical redundancy
  checks to ensure the integrity of the data contained in its chunks.

Published specification:
  Internet-Draft draft-boutell-png-spec-04.txt,
  "Png (Portable Network Graphics) Specification Version 1.0"
  which is an "rfc-to-be."  The IESG has concurred in publication of
  the spec as an Informational RFC; see item 11 of the IESG minutes
  for their meeting of 7-11-96.

Person & email address to contact for further information:
  Glenn Randers-Pehrson, randeg@alumni.rpi.edu or glennrp@arl.mil
  Thomas Boutell, boutell@boutell.com


