JPEG Network Graphics (JNG, ) is a

JPEG JPEG ( , short for Joint Photographic Experts Group and sometimes retroactively referred to as JPEG 1) is a commonly used method of lossy compression for digital images, particularly for those images produced by digital photography. The degr ...

-based

graphics file format An image file format is a file format for a digital image. There are many formats that can be used, such as JPEG, PNG, and GIF. Most formats up until 2022 were for storing 2D images, not 3D ones. The data stored in an image file format may be c ...

which is closely related to PNG: it uses the PNG file structure (with a different signature) as a

container format A container format (informally, sometimes called a wrapper) or metafile is a file format that allows multiple data streams to be embedded into a single file, usually along with metadata for identifying and further detailing those streams. Nota ...

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 (1, 2, 4, 8, 16-bit PNG, or 8-bit JPEG

grayscale image In digital photography, computer-generated imagery, and colorimetry, a greyscale (more common in Commonwealth English) or grayscale (more common in American English) image is one in which the value of each pixel is a single sample (signal), s ...

) for transparency information. However, a JNG may contain two separate JPEG datastreams for color information (one 8-bit and one 12-bit) to permit decoders that are unable to (or do not wish 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 (initially as part of the MNG specification). Usually, all the applications supporting the MNG file format can handle JNG files too. For example,

Konqueror Konqueror is a Free and open-source software, free and open-source web browser and file manager that provides World Wide Web, web access and file viewer, file-viewer functionality for file systems (such as local files, files on a remote FTP ser ...

has native MNG/JNG support, and MNG/JNG plugins are available for

Opera Opera is a form of History of theatre#European theatre, Western theatre in which music is a fundamental component and dramatic roles are taken by Singing, singers. Such a "work" (the literal translation of the Italian word "opera") is typically ...

Internet Explorer Internet Explorer (formerly Microsoft Internet Explorer and Windows Internet Explorer, commonly abbreviated as IE or MSIE) is a deprecation, retired series of graphical user interface, graphical web browsers developed by Microsoft that were u ...

, and

Mozilla Firefox Mozilla Firefox, or simply Firefox, is a free and open-source web browser developed by the Mozilla Foundation and its subsidiary, the Mozilla Corporation. It uses the Gecko rendering engine to display web pages, which implements curren ...

. The

Mozilla Application Suite The Mozilla Application Suite (originally known as Mozilla, marketed as the Mozilla Suite) is a discontinued cross-platform integrated Internet suite. Its development was initiated by Netscape Communications Corporation, before their acquisition ...

(and hence

Netscape Netscape Communications Corporation (originally Mosaic Communications Corporation) was an American independent computer services company with headquarters in Mountain View, California, and then Dulles, Virginia. Its Netscape web browser was o ...

) originally supported MNG/JNG, but native support was removed in Mozilla 1.5a by developers, and Mozilla has not supported the format since.

Safari A safari (; originally ) is an overland journey to observe wildlife, wild animals, especially in East Africa. The so-called big five game, "Big Five" game animals of Africa – lion, African leopard, leopard, rhinoceros, African elephant, elep ...

does not support MNG/JNG. JNG enhances the capabilities of the

JFIF The JPEG File Interchange Format (JFIF) is an image file format standard published as ITU-T Recommendation T.871 and ISO/IEC 10918-5. It defines supplementary specifications for the Digital container format, container format that contains the image ...

format (the usual JPEG file format) by supporting transparency, two consecutive color streams (one 8-bit and the other 12-bit), 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 (as an

alpha channel In computer graphics, alpha compositing or alpha blending is the process of combining one image with a background to create the appearance of partial or full transparency. It is often useful to render picture elements (pixels) in separate pass ...

) 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 (PNG-compressed) 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 In information and communications technology, a media type, content type or MIME type is a two-part identifier for file formats and content formats. Their purpose is comparable to filename extensions and uniform type identifiers, in that they ident ...

, but image/x-jng can be used.Official JNG specification
section 1

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: * JPEG XR: Supporting wide color space and a lossy format with transparency (JNG contender, standardized) *

WebP WebP is a raster graphics file format developed by Google intended as a replacement for JPEG, PNG, and GIF file formats. It supports both lossy and lossless compression, as well as animation and alpha transparency. Google announced the WebP ...

: Supporting a lossy format with transparency and animation (JNG/MNG contender, not yet standardized) *

JPEG XL The JPEG XL Image Coding System is a royalty-free open standard for a image compression, compressed Raster graphics, raster image format. It defines a graphics file format and the abstract device for coding JPEG XL bitstreams. It is developed by t ...

: Supporting wide color spaces, lossy and lossless encoding, animation and transparency (JPEG/PNG replacement contender)

Notes

External links

JNG 1.0 specification

Original JNG specification as part of the MNG specification

Photoshop Plugin (for Photoshop7.0 or greater)

Amiga Datatype (for AmigaOS 4.0 or greater)
{{DEFAULTSORT:Jpeg Network Graphics JNG Raster graphics file formats Portable Network Graphics