File Formats

MNGedit File Formats

MNGedit uses the PNG image file format for input and MNG image file format for output.

PNG

PNG (Portable Network Graphics) is an extensible file format for the lossless, portable, well-compressed storage of raster images. PNG provides a patent-free replacement for GIF and can also replace many common uses of TIFF. Indexed-color, grayscale, and truecolor images are supported, plus an optional alpha channel. Sample depths range from 1 to 16 bits.

PNG is designed to work well in online viewing applications, such as the World Wide Web, so it is fully streamable with a progressive display option. PNG is robust, providing both full file integrity checking and simple detection of common transmission errors. Also, PNG can store gamma and chromaticity data for improved color matching on heterogeneous platforms.

The PNG format was approved in October 1996 by the W3C (World Wide Web Consortium) as a W3C Recommendation and has also been published as RFC-2083. The PNG specification is on a standards track under the purview of ISO/IEC JTC 1 SC 24 and is expected to be released eventually as ISO/IEC International Standard 15948.

There is a World Wide Web site for PNG at http://www.cdrom.com/pub/png/. This is a central location for current information about PNG and PNG-related tools.

MNG

MNG (Multiple-image Network Graphics) is a multiple-image member of the PNG format family. It can contain animations, slide shows, or complex still frames, comprised of multiple PNG or JNG single-image datastreams. The MNG format uses the same chunk structure that is defined in the PNG specification, and it shares other features of the PNG format.

On January 11, 2001, the PNG Development Group approved the MNG-1.0 and JNG-1.0 (JPEG Network Graphics) specifications.

In addition to MNG itself, two subset formats have also been defined, namely MNG-LC (Low Complexity) and MNG-VLC (Very Low Complexity). These are proper subsets of MNG without the reusable-object, Delta-PNG, and LOOP capability, which can be used for simple animations, storage of multiple-page fax documents, and the like.

MNGedit produce simplified MNG-VLC output file with sequences of chunks:

MHDR

FRAM - IHDR -IEND

...

MEND

PNGplay supports only the subset of the MNG format generated by the utility PNGtoMNG and by MNGedit. All MNG chunks except MHDR, TERM, FRAM, IHDR-IEND, MEND will be skipped. Delta-PNG is not supported.