JPEG Network Graphics


JPEG Network Graphics is a JPEG-based graphics file format which is closely related to PNG: it uses the PNG file structure as a container format to wrap JPEG-encoded image data.
JNG was created as an adjunct to the MNG animation format, but may be used as a stand-alone format. JNG files embed an 8-bit or 12-bit JPEG datastream in order to store color data, and may embed another datastream for transparency information. However, a JNG may contain two separate JPEG datastreams for color information to permit decoders that are unable to handle 12-bit datastreams to display the 8-bit datastream instead, if one is present.
Version 1.0 of the JNG specification was released on January 31, 2001. Usually, all the applications supporting the MNG file format can handle JNG files too. For example, Konqueror has native MNG/JNG support, and MNG/JNG plugins are available for Opera, Internet Explorer, and Mozilla Firefox. The Mozilla Application Suite originally supported MNG/JNG, but native support was removed in Mozilla 1.5a by developers, and Mozilla has not supported the format since, despite requests from its users. Safari does not support MNG/JNG.
JNG enhances the capabilities of the JFIF format by supporting transparency, two consecutive color streams, and other useful PNG features like color correction, gamma correction, embedded color profiles, PNG-style metadata, checksums, etc. The transparency information inside a JNG file can be saved either in lossless PNG format or in lossy JPEG format. This way, users can benefit from the power of JPEG compression while preserving lossless transparency information.
The chunk-based structure of JNG files is essentially the same as that of PNG files, differing only in the slightly different signature and the use of different chunks.
JNG does not have a registered Internet media type, but image/x-jng can be used.

Alternatives

Due to the lack of wide adoption of both the JNG and MNG format, it has fallen in disuse in favor of other formats that are in active development with similar qualities: