||This article includes a list of references, but its sources remain unclear because it has insufficient inline citations. (June 2008)|
|Developer(s)||Independent JPEG Group|
|Initial release||October 7, 1991|
|Stable release||9 / January 13, 2013|
|License||Custom free software license; can be used in any application without royalty, with acknowledgment.|
libjpeg is a widely-used free software library written in C which implements JPEG decoding and encoding functions alongside various utilities for handling JPEG images. This library is maintained by the Independent JPEG Group (IJG), an informal organization which is not affiliated with the JPEG ISO committee.
The Open Source software implementation of the Independent JPEG Group (IJG), as well as being one of the major Open Source packages, was key to the success of the JPEG standard and was incorporated by many companies into a variety of products such as image editors and Internet browsers.
The widely used IJG implementation was first publicly released in October 1991 and has been considerably developed since that time. JPEG JFIF images are widely used on the Web. The amount of compression can be adjusted to achieve the desired trade-off between file size and visual quality.
The following utility programs are available with libjpeg:
- cjpeg and djpeg, for performing conversions between JPEG and some other popular image file formats.
- rdjpgcom and wrjpgcom, for inserting and extracting textual comments in JPEG files.
- jpegtran – a utility for lossless transcoding between different JPEG formats.
The jpegtran command-line program is useful to:
- optimize the Huffman coding layer of a JPEG file to increase compression,
- convert to JPEG Arithmetic coding to further increase compression (and back),
- convert between progressive and non-progressive JPEG formats,
- eliminate non-standard application-specific data inserted by some image programs, or
- to perform certain transformations on a file, such as:
There is an associated Windows application, Jpegcrop, which provides a user interface to jpegtran.
Version roadmap 
There are currently two conditions which trigger a major version bump of the JPEG library:
- New types of files can be created which are not compatible with prior releases, and
- Changes in the master records which break the binary compatibility (usually addition of entries for new functions).
In all major upgrades since v6 both conditions 1. and 2. came together, while the source compatibility (API) could largely be retained.
|Major version||New file format feature||New master record entries||References|
|Old version, no longer supported: 6||progressive JPEG support||progressive_mode ...||ITU-T Recommendation T.81
ISO/IEC IS 10918-1
|Old version, no longer supported: 7||arithmetic coding support||scale_num/scale_denom for
compression (encoding) ...
|ITU-T JPEG-Plus Proposal ...|
|Old version, no longer supported: 8||SmartScale
(variable block size)
|block_size/lim_Se etc.||Evolution of JPEG |
|Current stable version: 9||internal color transform
(FF F8 LSE extension marker)
|color_transform||JPEG 9 Lossless Coding 
InfAI JPEG Development Site 
|Legend:||Old version||Older version, still supported||Current version||Latest preview version||Future release|
For version 7 both conditions were different subjects (arith_code entry already existed), other versions are same subject.
libjpeg-turbo is a fork of libjpeg that uses SIMD instructions to accelerate baseline JPEG encoding and decoding. Many projects are now using libjpeg-turbo instead of libjpeg, including Fedora (since Fedora 14), Mozilla (since Firefox 5.0, while Firefox 13.0 gained additional performance by adding the accelerated Huffman coding routines from libjpeg-turbo 1.2.0, which were previously excluded due to a license conflict), and Google Chrome (since version 11). Apart from performance, some projects have chosen to use libjpeg-turbo because it allows them to retain backward ABI compatibility with the older libjpeg v6b release. Both libjpeg v7 and v8 broke ABI compatibility with prior releases.
libjpeg-turbo can be configured to be compatible with the libjpeg v7 or v8 ABI, but it does not implement the complete set of features in recent IJG releases, including the SmartScale format extension. The libjpeg-turbo Project has chosen not to support SmartScale, citing concerns regarding the fact that it is not an ITU-T standard and citing their own research that questions the usefulness of the feature. By extension, since the only major new feature in libjpeg v9 is specific to the SmartScale format, The libjpeg-turbo Project has chosen to forgo emulating libjpeg v9. Therefore, SmartScale files created by libjpeg v7 and later will not be readable by libjpeg-turbo, or they will not be decompressed correctly.
See also 
- "JPEG homepage".
- "JPEG JFIF".
- "Jpegcrop Preferences and Options description".
- "Filmic Games >> The greatest failure of our patent system was...".
- "680385 - Firefox does not show arithmetic coded jpegs".
- "New jpegtran features".
- Contributed document - Word .doc file: ITU-T JPEG-Plus Proposal R3
- Contributed document - Word .doc file: Evolution of JPEG
- Contributed document - Word .doc file: JPEG 9 Lossless Coding
- News c't magazine 2012 issue 18 page 43, Software Links
- Software That Uses or Provides libjpeg-turbo. February 9, 2012.
- Issue 48789 – chromium – Use libjpeg-turbo instead of libjpeg. April 14, 2011.
- Bug 698519 – Update to libjpeg-turbo 1.2. February 28, 2012
- libjpeg for F14. February 9, 2012.
- libjpeg: API changes/compatibility. February 9, 2012
- libjpeg-turbo README file
- "What About libjpeg v9?". libjpeg-turbo team. Retrieved 8 February 2013.
- Official website
- Binary package of libjpeg for Microsoft Windows (at GnuWin32 in SourceForge)
- Binary packages of libjpeg for Microsoft Windows (MinGW and Microsoft Visual C++ versions 7 and 8), and for Mac OS X (Universal, GCC 4.0; PowerPC, GCC 4.0; PowerPC, GCC 3.3) at ClanLib
- libjpeg-turbo, an ABI-/API-compatible fork of libjpeg that uses x86 SIMD instructions to achieve a substantial speedup over the reference implementation.
- JPEG FAQs
- Additional features for libjpeg