PNG: The Definitive Guide

Chapter 12. Multiple-image Network Graphics

The Multiple-image Network Graphics format, or MNG, is not merely a multi-image, animated extension to PNG; it can also be used to store certain types of single images more compactly than PNG, and in mid-1998 it was extended to include JPEG-compressed streams. Conceivably, it may one day incorporate audio or even video channels, too, although this is a more remote possibility. Yet despite all of this promise--or, rather, because of it--MNG was still a slowly evolving draft proposal nearly four years after it was first suggested.

As noted in Chapter 7, “History of the Portable Network Graphics Format”, MNG's early development was delayed due to weariness on the part of the PNG group and disagreement over whether it should be a heavyweight multimedia format or a very basic “glue” format. What it has evolved into, primarily due to the willingness of Glenn Randers-Pehrson to continue working on it, is a moderately complex format for composing images or parts of images, either spatially or temporally, or both. I will not attempt to describe it in full detail here--a complete description of MNG could fill a book all by itself and probably will, one of these days--but I will give a solid overview of its basic features and most useful applications. Further information on the format can be found at the MNG web site, http://www.libpng.org/pub/mng/.

12.1. Common Applications of MNG

Perhaps the most basic, nontrivial MNG application is the slide ...