APNG

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Animated Portable Network Graphics
File extension:	`.png`
Type of format:	animated PNG
Extended from:	PNG

The APNG (Animated Portable Network Graphics) file format is an extension to the Portable Network Graphics (PNG) specification proposed by Stuart Parmenter and Vladimir Vukicevic of the Mozilla Corporation. It allows for animated PNG files that work similarly to animated graphics interchange format (GIF) files, while retaining backward compatibility with non-animated PNG files.

The first frame on an APNG file is stored as a normal PNG stream, and so most old PNG decoders will be able to display the first frame of an APNG file. The frame speed data and extra animation frames are stored in extra chunks (as provided for by the original PNG specification).

MNG is another animated image format closely related to PNG. APNG's advantage is the smaller library size and defacto compatibility with older PNG implementations.

1 History
2 See also
3 References
4 External links

[edit] History

The APNG specification was created in 2004. After a failed attempt to get APNG added directly to Mozilla, its authors worked on adding APNG support to the ubiquitous libpng instead. This was completed in 2006 and once again was proposed for addition to Mozilla. Its main purpose is said to be in GUI and XUL application usage, but open usage on the Web is also expected. Mozilla Firefox eventually added support for APNG in Firefox 3.0 trunk builds on 23 March 2007.^[1]

Among the maintainers of the PNG and MNG formats APNG was not received that well for several reasons. MNG provides all the features APNG provides, but is not supported at all by PNG-only decoders. To work around this APNG specifications violate the PNG specification. APNG would be compatible to the PNG spec with minor alterations also concerning its signature and intended MIME type, but these would break the desired backwards compatibility in many circumstances. During the final process of aligning the specifications in March 2007 alternative approaches were also discussed. The proposals of John Bowler and “Adeluc” et al., called “mPNG”, are based on the concept of sprites in one large standard PNG image, whereas APNG encodes a number of separate images. Another way suggested was adding APNG chunks into AGIFs.