Animated PNG?

Two Mozilla hackers, Vladimir Vukićević and Stuart “Pavlov” Parmenter, have put together a spec for an animated PNG (aPNG) format. Wait a second, isn’t there already a format for animated PNG called MNG? Yes. Yes, there is.


Up to version 1.4, Mozilla and browsers based on it such as Netscape 6 and 7 supported MNG. MNG support was removed from Mozilla for a number of reasons, many of which were disputed at the time. Among the reasons were a large file size and a lack of a Mozilla maintainer for the code. Work has continued on the code and if it were included in Mozilla again now, it would be significantly smaller than what shipped with Mozilla 1.4. But it seems to not be enough. Back in Aug 2003, Stuart Parmeter dictated what it would take for MNG to be restored. We’re closer, but I wonder whether the requirements were realistic.

What Now?

So where’s that leave us? The problem with the removal of MNG is that there is no other graphics format that can completely replace it. MNG provided all the beauty of PNG — a full range of transparency, true color support, etc. — as well as animation. In addition, the subformat of MNG, JNG, supported embedding JPEG images for better compression of photographic content while also allowing a full range of transparency. Mozilla practically needs something like MNG for internal use in skins and themes. Indeed, when MNG was removed, a number of themes needed to be updated with GIF-replacements that were larger in size and didn’t look as clean due to the limited color palette of GIF.

If all that was needed was something for Mozilla themes, I’d question the need for revising the PNG file format; it’s clear that MNG/JNG would do what we need today. But I believe the Mozilla drivers are looking to create something that is backward compatible and usable on the web now. It seems that the primary advantage to aPNG is that they are trying to design it so that it will at worst show up as a static PNG image in apps that do not support animation. In real terms this means that IE users as well as web development tools such as Dreamweaver would at least see a PNG image. Another benefit of aPNG over MNG is that it should be a minor change to the PNG library and therefore easier to maintain.

It’s exciting to see Mozilla developers working with the original authors of the PNG specification. Thomas Boutell, the instigator and original editor of the PNG spec writes MNG is dead, long live APNG. Calling the Mozilla pair “young turks”, he speaks positively about their efforts to work with the “old-timers” to create a simple animated PNG format. He says “I could not be more pleased with this development.”

Once the format is defined tools need to support it. At the moment I can create a MNG simply by saving my animation in Jasc Paint Shop Pro. How long before I can do the same with aPNG?