MNG

~ the goodbye ~

The animation format I actually used was the GIF, in a forum signature on DonanımHaber or frmtr, sitting under a list of whatever parts were in my machine that year. Everybody did. A signature was two hundred pixels of looping something, and the file that carried it was a GIF, because that was the only animated thing a browser would draw without being asked. MNG was the format that was meant to replace it, and I could not have used one if I had wanted to.

It came out of a principle rather than a product plan. When PNG was being designed in early 1995 the group deliberately left animation out, on the argument that overloading one file type with both stills and movies is bad for users, who then cannot tell what a file is, and bad for servers, which ought to send image/ for one thing and video/ for the other. So animation got its own format. Multiple-image Network Graphics was a container that held PNG frames, or JNG frames when you wanted lossy ones, with its own eight byte signature and a much larger vocabulary of chunks for timing and layering. Version 1.0 of the specification was published on 31 January 2001.

It beat the GIF in every direction that mattered. True color where the GIF had 256 palette entries, and alpha transparency where the GIF had one knocked-out color. It also carried enough sequencing control to build something closer to a small animation engine than a flipbook. The complexity had a price, and the price is the whole story: the specification was large enough that its own authors defined two cut-down profiles, MNG-LC and MNG-VLC, so an implementer could claim partial support without writing the entire thing.

Almost nobody wrote even the partial thing. Netscape 6 and 7 shipped MNG natively and so did the Mozilla suite behind them, Konqueror carried it for a while, and that is the list of browsers. Internet Explorer never had it, and neither did Opera or Safari. Chrome did not exist yet and was never going to add it. Web servers did not ship with a MIME type configured for the format either, so even a site that wanted to serve a .mng had to go and edit a config file first.

~ the chronicle ~

~ the decision not to animate PNG ~

It is worth being fair to the 1995 reasoning, because it was not foolish. A file called cat.png that might silently turn out to be a thirty second movie is a worse thing to hand a user than two file types with two names. The group chose clarity and paid for it with a format that had to win adoption from nothing, against an incumbent already sitting in every browser. The LZW patents that had made GIF legally awkward then expired, which removed the last standing argument for switching at all.

~ bug 195280 ~

On 27 February 2003 a Mozilla developer opened a bug titled "Removal of MNG/JNG support" and laid out the numbers. On Linux the MNG decoder was libimgmng.so at 241,492 bytes against libimglib2.so at 261,796 bytes, so one unused format cost nearly as much as every other image decoder plus the imaging logic combined. On Windows the comparison was worse: imgmng.dll at 170,336 bytes against imglib2.dll at 155,024, which made the MNG decoder the larger of the two. He added that the integration was rough and that nobody active was maintaining it. Animated GIF and Flash, he noted, already covered most of what MNG offered.

The thread ran to a hundred and thirty one comments and the first three arrived within ninety minutes. "Please, no. Personally, I'm just starting to use JNG. MNG is apparently popular in Asia. It's in, it works, let's leave it in." Then: "Why not just disable by default, instead of removing?" Then Glenn Randers-Pehrson, who had been building these formats since the PNG days: "Nice timing, only 3-1/2 months before we could unveil MNG-LZW." The bug was marked FIXED on 3 June 2003 and verified three weeks after that. A separate bug asking for the support to be restored was filed and stayed open for years.

~ the format Mozilla built instead ~

What came next still reads as a small cruelty. Having removed MNG for being too large, Mozilla went and designed APNG, an animated PNG in a single file, backward compatible so that a decoder which does not understand the animation chunks simply shows the first frame. That is the design the PNG group had rejected on principle in 1995, built by the organization that had been the format's only serious implementer, and it is in every browser today.

MNG itself never quite stopped existing. ImageMagick writes it, GIMP exports it, IrfanView reads it with a plugin, and MPlayer will play one if it was linked against libmng. There was even a Mozilla fork called MNGzilla that carried the decoder forward for the people who wanted it, and the project notes record it as dormant since 2007. A format with a published specification and free implementations does not disappear. It just stops being something you can put on a page.

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