A file with .mng extension is a Mutliple-image Network Graphics file format that is similar to PNG image format but supports animated images. It was developed to avoid overloading the PNG format with additional feature of animations. MNG is also similar to GIF files but uses more compression and supports full alpha feature. The unofficial MIME media type for MNG files is video/x-mng. MNG files can be opened in applications such as ImageMagik and IrfanView.
MNG File Format
MNG file format is similar to that of PNG and uses the same chunk structure as defined in the PNG specifications. A MNG decoder must be able to decode the PNG datastreams without specifying any special flags for decoding instructions. MNG groups multiple images together into a “frame”, with some images used as sprite for moving from one location to another. The mechanism allows reusing image data without retransmitting it. The MNG specifications can be referred to for developer’s reference.
The MNG datastream begins with an 8-byte signature containing:
138 77 78 71 13 10 26 10 - (decimal)
8a 4d 4e 47 0d 0a 1a 0a - (hexadecimal)
\212 M N G \r \n \032 \n - (ASCII C notation)
This is similar to that of PNG signature but contains MNG instead of PNG.
An MNG frame consists of two-dimensional image of smaller images. Each small image can be accessed using the row and column index combination. The format is capable of storing three-dimensional “voxel” data that is arranged a series of two-dimensional planes. Each plane is represented by a PNG or Delta-PNG datastream. Each Delta-PNG datastream defines an image as the differences from the parent PNG image. This provides a much more compact way of representing subsequent images than using a complete PNG datastream for each.