GIF

Animated GIFs need a spec that, in particular, specifies how to handle timings (not all browsers honor all values, so we should specify what needs to be honored exactly)

Implementations

Gecko

• http://mxr.mozilla.org/mozilla-central/source/image/decoders/nsGIFDecoder2.h
• http://mxr.mozilla.org/mozilla-central/source/image/decoders/GIF2.h
• http://mxr.mozilla.org/mozilla-central/source/image/decoders/nsGIFDecoder2.cpp

WebKit

• http://trac.webkit.org/browser/trunk/Source/WebCore/platform/image-decoders/gif/GIFImageDecoder.h
• http://trac.webkit.org/browser/trunk/Source/WebCore/platform/image-decoders/gif/GIFImageReader.h
• http://trac.webkit.org/browser/trunk/Source/WebCore/platform/image-decoders/gif/GIFImageDecoder.cpp
• http://trac.webkit.org/browser/trunk/Source/WebCore/platform/image-decoders/gif/GIFImageReader.cpp
• http://trac.webkit.org/browser/trunk/Source/WebCore/platform/image-decoders/ImageDecoder.cpp

Blink

• https://chromium.googlesource.com/chromium/blink/+/master/Source/core/platform/image-decoders/gif/GIFImageDecoder.h
• https://chromium.googlesource.com/chromium/blink/+/master/Source/core/platform/image-decoders/gif/GIFImageReader.h
• https://chromium.googlesource.com/chromium/blink/+/master/Source/core/platform/image-decoders/gif/GIFImageDecoder.cpp
• https://chromium.googlesource.com/chromium/blink/+/master/Source/core/platform/image-decoders/gif/GIFImageReader.cpp
• https://chromium.googlesource.com/chromium/blink/+/master/Source/core/platform/image-decoders/ImageDecoder.cpp

Other

• http://sourceforge.net/p/giflib/code/ci/master/tree/ (giflib)
• https://github.com/jnordberg/gif.js (gif.js)
• https://github.com/deanm/omggif (omggif)
• https://github.com/avik-das/giferly (giferly)
• http://code.google.com/p/gifdotnet/source/browse/ (gifdotnet)

References

Specifications

• GIF87a: Text (Stanford) / Text (W3C)
• GIF89a: Text / HTML
• GIF Application Extensions:
  • NETSCAPE 2.0
    • GIF Application Extension: NETSCAPE2.0
    • Netscape Looping Application Extension
    • Netscape Buffering Application Extension
  • ANIMEXTS 1.0
    • AnimExts Looping Application Extension
  • ICCRGBG1 012
    • Specification ICC.1:2004-10 (Profile version 4.2.0.0) – Image technology colour management: Architecture, profile format, and data structure (section B.6)
  • XMP Data XMP
    • XMP Specification, Part 3: Storage in Files (section 1.1.2)
  • fractint 001 / fractint 002 / fractint 003 / fractint 004 / fractint 005 / fractint 006 / fractint 007
    • fractint encoder source code
    • fractint decoder source code, with notes and backwards compatibility for older versions of the fractint extension blocks. All of their extension blocks have names of the form fractintnnn, where nnn is a 3 digit block number.
  • MathType 001 / MathType 002 / MathType 003
    • MathType baseline information
    • MathType: GIFs do not retain their DPI properties - descriptions and sample images could be used to reverse engineer format

Further details

• Wikipedia:GIF
• GIF File Format
• What's in a GIF
• Command Line Fanatic: Inside the GIF file format
• Gifology: Understanding GIF Files & GIF Animation
• All About GIF89a

Test images

• ImageTestSuite
  • Documentation
  • Images (Archive)
  • Images (git)