CGM to MNG Converter

MNG (Multiple-image Network Graphics) is an animation and multiple-image format designed as the animated counterpart to PNG, with its specification reaching version 1.0 on January 31, 2001. Developed by Glenn Randers-Pehrson and members of the PNG development community, MNG extends PNG's capabilities with support for frame-based animation sequences, slide shows, complex sprite overlays, and JNG (JPEG Network Graphics) frames for lossy compression of photographic content within the same container. An MNG file consists of a series of chunks (following PNG's chunk-based architecture): MHDR and MEND chunks bookend the datastream, with embedded PNG or JNG images as individual frames and control chunks (DEFI, FRAM, LOOP, ENDL, TERM, BACK, BASI, CLON, PAST, DISC, SHOW) directing playback timing, looping behavior, layer compositing, and memory management. The format supports both full-frame replacement and delta (difference) updates for efficient encoding of animations with static backgrounds, as well as object-based animation where sprites are defined once and repositioned across frames. One advantage is technical sophistication: MNG provides a level of animation control that GIF and APNG cannot match — frame-accurate timing, nested loops, conditional branches, interframe compression, and mixed lossy/lossless content within a single animation. The PNG-based foundation ensures lossless quality with full alpha transparency for each frame. MNG is supported by ImageMagick, GIMP, and various media players, though browser support was limited, which led to APNG's emergence as a simpler alternative for web animation.