Register of public PNG chunks and keywords, Version 1.5.0

The latest versions of this document, the PNG specification, and related information can always be found at the PNG FTP archive sites, ftp://ftp.simplesystems.org/pub/png/ and http://libpng.download/. The maintainers of the PNG specification can be contacted by e-mail at png-mng-misc @ lists.sourceforge.net.

Abstract

This document is the register of public chunks and keywords in the Portable Network Graphics (PNG) specification, version 1.2 [PNG-1.2], and in Portable Network Graphics (PNG) Specification (Second Edition) [PNG-ISO], plus any additional registered "public" PNG chunks and keywords, with their date of registration and location of their specifications.

Some chunks listed here are expected to be less widely supported than those defined in the basic specification. However, application authors are encouraged to use these chunk types whenever appropriate for their applications.

Additional chunk types and keywords may be proposed for inclusion in these lists by contacting the PNG specification maintainers at png-mng-misc @ lists.sourceforge.net.

Table of Contents

1. Register of Public PNG Chunks
2. Register of Public Text Chunk Keywords
3. Appendix: Revision History
4. References
5. Credits

1. Register of Public PNG Chunks

This table lists the registered public PNG chunks.

   Chunk    Date       Formal specification
   type   registered   of chunk type
   
   IDAT    7 Mar 95    PNG 1.2
   IEND    7 Mar 95    PNG 1.2
   IHDR    7 Mar 95    PNG 1.2
   PLTE    7 Mar 95    PNG 1.2
   
   bKGD    7 Mar 95    PNG 1.2
   cHRM    7 Mar 95    PNG 1.2
   dSIG    1 May 08    PNGEXT 1.4.0
   eXIf   13 Jul 17    PNGEXT 1.5.0
   fRAc    7 Mar 95[1] PNGEXT 1.2.0
   gAMA    7 Mar 95    PNG 1.2
   gIFg    7 Mar 95    PNGEXT 1.2.0
   gIFt    7 Mar 95[2] PNGEXT 1.2.0
   gIFx    7 Mar 95    PNGEXT 1.2.0
   hIST    7 Mar 95    PNG 1.2
   iCCP   17 Aug 98    PNG 1.2
   iTXt    9 Feb 99    PNG 1.2
   oFFs    7 Mar 95    PNGEXT 1.2.0
   pCAL   28 Jan 97    PNGEXT 1.2.0
   pHYs    7 Mar 95    PNG 1.2
   sBIT    7 Mar 95    PNG 1.2
   sCAL    7 Mar 95    PNGEXT 1.2.0
   sPLT    9 Dec 96    PNG 1.2
   sRGB    6 Nov 96    PNG 1.2
   sTER   15 Apr 06    PNGEXT 1.3.0
   tEXt    7 Mar 95    PNG 1.2
   tRNS    7 Mar 95    PNG 1.2
   zTXt    7 Mar 95    PNG 1.2
   
   [1] The fRAc chunk was registered but never formally specified.
   [2] The gIFt chunk was formally deprecated on 23 Oct 98.

2. Register of Public Text Chunk Keywords

This table lists the keywords that have been registered for use in PNG textual chunks.

   Keyword           Date         Formal specification
                  registered      of keyword
   
   Title           7 Mar 95       PNG-1.2
   Author          7 Mar 95       PNG-1.2
   Description     7 Mar 95       PNG-1.2
   Collection     24 Jul 04       png-list archives
   Copyright       7 Mar 95       PNG-1.2
   Creation Time   7 Mar 95       PNG-1.2
   Software        7 Mar 95       PNG-1.2
   Disclaimer      7 Mar 95       PNG-1.2
   Warning         7 Mar 95       PNG-1.2
   Source          7 Mar 95       PNG-1.2
   Comment         7 Mar 95       PNG-1.2

All registered textual keywords in iTXt and all other chunk types are limited to the ASCII characters A-Z, a-z, 0-9, space, and the following 20 symbols:

   ! " % & ' ( ) * + , - . / : ; < = > ? _

but not the remaining 12 symbols:

   # $ @ [ \ ] ^ ` { | } ~

This restricted set is the ISO-646 "invariant" character set [ISO-646]. These characters have the same numeric codes in all ISO character sets, including all national variants of ASCII.

3. Appendix: Revision History

4. References

[ISO/IEC-8859-1]
International Organization for Standardization and International Electrotechnical Commission, "Information Technology--8-bit Single-Byte Coded Graphic Character Sets--Part 1: Latin Alphabet No. 1", IS 8859-1, 1998.
Also see sample files at
ftp://ftp.simplesystems.org/pub/png/documents/iso_8859-1.*

[ISO-646]
International Organization for Standardization and International Electrotechnical Commission, "Information Technology--ISO 7-bit Coded Character Set for Information Exchange", 1991.

[PNG-1.2]
Randers-Pehrson, G., et. al., "PNG (Portable Network Graphics Format) Version 1.2", which is available at
http://libpng.download/documents/.

[PNG-ISO]
"Portable Network Graphics (PNG) Specification (Second Edition)," 10 November 2003, also released as "International Standard 15948:2003 -- Portable Network Graphics (PNG): Functional specification", available at http://png-mng.sourceforge.net/pub/png/spec/iso/

[PNGEXT-1.2.0]
Randers-Pehrson, G., et. al., "Extensions to the PNG (Portable Network Graphics Format) Version 1.2.0", which is available at
http://libpng.download/documents/history/.

[PNGEXT-1.3.0]
Randers-Pehrson, G., et. al., "Extensions to the PNG (Portable Network Graphics Format) Version 1.3.0", which is available at
http://libpng.download/documents/history/.

[PNGEXT-1.4.0]
Randers-Pehrson, G., et. al., "Extensions to the PNG (Portable Network Graphics Format) Version 1.4.0", which is available at
http://libpng.download/documents/history/.

[PNGEXT-1.5.0]
Randers-Pehrson, G., et. al., "Extensions to the PNG (Portable Network Graphics Format) Version 1.5.0", which is available at
http://libpng.download/documents/.

5. Credits

Editor

Copyright Notice

Copyright © 2000, 2006-2008, 2013, 2017 by: Glenn Randers-Pehrson

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End of Register of Public PNG Chunks and Keywords 1.5.0