 | |
| Original author(s) | Tom Lane |
|---|---|
| Developer(s) | |
| Initial release | October 7, 1991; 33 years ago (1991-10-07) |
| Stable release | |
| Repository | www |
| Written in | C |
| Operating system | Cross-platform |
| Type | library |
| License | CustomBSD-like (free software) |
| Website | |
libjpeg is a freelibrary withfunctions for handling theJPEG image data format. It implements a JPEGcodec (encoding and decoding) alongside various utilities for handling JPEG data.It is written inC and distributed asfree software together with itssource code under the terms of a custompermissive (BSD-like) free software license, which demandsattribution.The original variant is maintained and published by the Independent JPEG Group (IJG). Meanwhile, there are severalforks with additional features.
JPEGJFIF 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.[4]
The following utility programs are shipped together with libjpeg:
Thecommand-line programjpegtran provides several features for reformatting and recoding the representation of theDCT coefficients, for transformation of actual image data and for discarding auxiliary data in JPEG files, respectively. The transformations regarding the representation of the coefficients comprise:
These transformations are each completely lossless and reversible. The transformations on the image data comprise:
These arelossless and reversible only regarding the image data that is kept. Reencoding with repeated lossy quantisation of the image data (generation loss) does not take place.
The JPEG implementation of the Independent JPEG Group (IJG) was first publicly released on 7 October 1991 and has been considerably developed since that time.The development was initially mainly done byTom Lane.Theopen-source implementation of the IJG was one of the major open-source packages and was key to the success of the JPEG standard. Many companies incorporated it into a variety of products such as image editors and web browsers.[9]
For version 5, which was released on September 24, 1994, the whole code base was rewritten. It introduced the utility programsrdjpgcom andwrjpgcom for handling embedded text comments.The version 6 from 2 August 1995 came with support for progressive JPEG and for the first time with the utility programjpegtran. This utility was extended with features to rotate and flip images and grayscale reduction in version 6b.
From version 6b of libjpeg of 27 March 1998, Miyasaka Masaru forked a branch namedlibjpeg/SIMD, which included x86 SIMD optimisations. It got substantial contributions from the TigerVNC and the VirtualGL projects in 2009. On that basis the libjpeg-turbo project was created in 2010.[10]
On 4 March 2014, the first version of the filesize-optimising forkMozJPEG was published. For this version Josh Aas from Mozilla Research reworked thePerl scriptjpegcrush fromx264's main developer Loren Merritt and integrated it into the code base of libjpeg-turbo.[11]
On 10 July 2014, Mozilla released version 2.0, which mainly added trellis quantisation and is now able to reduce the size of baseline JPEGs also.Facebook, Inc. donated60000 dollars for the development of the next version,[12] andCloudFlare assigned a developer for the improvement of MozJPEG.[13]
In 2019, libjpeg-turbo became the ISO and ITU endorsed reference implementation for the JPEG format.[14]
In April 2024, Google introducedJpegli, a new JPEG coding library that offers enhanced capabilities and a 35% compression ratio improvement at high quality compression settings, while the coding speed is comparable with MozJPEG.[15]
After 11 years and a change in leadership, the IJG under Guido Vollbeding released new versions of libjpeg (7 through 9), of which each broke ABI compatibility with previous versions.[16] The changes that were held in prospect after the 6x series were not delivered.[17]In version 7, support forarithmetic coding was introduced, which earlier has been rejected because of thepatent situation, as well as the crop feature in jpegtran (-crop).[17]
Versions 8 and 9 served basically for the introduction of controversial[18] incompatible format extensions. These are widely regarded as ineffective and inferior to existing, standardised solutions.[19] Their standardisation was rejected after submission to theITU-T. The original organiser Tom Lane and others criticize these changes as a break from the goals of the IJG.[18]
| Version | Released | New features | |
|---|---|---|---|
| ITU T.81 JPEG Compatible | |||
| Old version, not maintained: 1 | 1991 |
| |
| Old version, not maintained: 2 | 1991 |
| |
| Old version, not maintained: 3 | 1992 | Internal and image quality improvements | |
| Old version, not maintained: 4 | 1992 | Internal and speed improvements | |
| Old version, not maintained: 4a | 1993-02-18 | ||
| Old version, not maintained: 5 | 1994-09-24 | Internal improvements and revised API | |
| Old version, not maintained: 5a | 1994-12-07 | ||
| Old version, not maintained: 5b | 1995-03-15 | ||
| Old version, not maintained: 6 | 1995-08-02 |
| |
| Old version, not maintained: 6a | 1996-02-07 | ||
| Old version, still maintained: 6b | 1998-03-27 |
(used bylibjpeg-turbo,MozJPEG andJpegli) | |
| Old version, not maintained: 7 | 2009-06-27 | ||
| Proprietary non-compatible extensions | |||
| Old version, not maintained: 8 | 2010-01-10 | ||
| Old version, not maintained: 8a | 2010-02-28 | RGBA | |
| Old version, not maintained: 8b | 2010-05-16 | Memory corruption & build fixes | |
| Old version, not maintained: 8c | 2011-01-16 | Option for selecting DCT block size (SmartScale) | |
| Old version, not maintained: 8d | 2012-01-15 | RGB JPEG (no color transform to YCbCr) | |
| Old version, not maintained: 9 | 2013-01-13 | ||
| Old version, not maintained: 9a | 2014-01-19 | ||
| Old version, not maintained: 9b | 2016-01-17 | Computation improvements | |
| Old version, not maintained: 9c | 2018-01-14 | jpegtran -wipe | |
| Old version, not maintained: 9d | 2020-01-12 |
| |
| Old version, not maintained: 9e | 2022-01-16 | ARM and ARM64 support (MSVC) | |
| Latest version:9f | 2024-01-14 |
| |
Well-known forks are libjpeg-turbo, which optimises for speed of execution, and MozJPEG, which optimises for smaller file sizes.
There is also asimilarly named library from theISO, which aims to be a complete implementation of JPEG,JPEG XT andJPEG LS standards.[25]
 | |
| Developer(s) | libjpeg-turbo Project |
|---|---|
| Initial release | November 19, 2010; 14 years ago (2010-11-19) |
| Stable release | |
| Repository | github |
| Website | libjpeg-turbo |
libjpeg-turbo is afork of libjpeg that usesSIMDinstructions to accelerate baseline JPEG encoding and decoding. Many projects are now using libjpeg-turbo instead of libjpeg, including popular Linux distributions (Fedora,Debian,Mageia,openSUSE, ...),Mozilla, andChrome.[27][28][29] Apart from performance, some projects have chosen to use libjpeg-turbo because it allows them to retain backwardABI compatibility with the older libjpeg v6b release.[30] libjpeg v7, v8 and v9 broke ABI compatibility with prior releases.[16]
libjpeg-turbo implements the standard-compliant arithmetic coding and lossless crop features seen in libjpeg v7. It can also be configured to be compatible with the libjpeg v7 or v8 ABI, but it does implement DCT scaling and the proprietary SmartScale, which builds on DCT scaling.[31] libjpeg-turbo chooses not to support SmartScale, because it is not anITU-T standard and because their own research finds it (and DCT scaling) ineffective.[21] 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.[citation needed]
Since 2019, libjpeg-turbo is one of the two JPEG reference implementations, available as ISO/IEC 10918-7 and ITU-T T.873.[14] The other reference implementation is ISO libjpeg which also includes support for JPEG XT and JPEG LS.[citation needed]
 | |
 MozJPEG tries several partitionings of the spectrum of DCT coefficients | |
| Developer(s) | Mozilla Research |
|---|---|
| Initial release | March 4, 2014; 11 years ago (2014-03-04) |
| Stable release | |
| Website | github |
MozJPEG is a fork from libjpeg-turbo done by Josh Aas and others from Mozilla Research. It aims to speed up loading times of webpages by achieving a reduction in file size (of about 10%) and therefore transmission time through improvement of coding efficiency while retaining image quality. To achieve this, it uses more processing power for the encoding (asymmetry) while retaining full compatibility with the JPEG standard and requiring no changes on the decoder side.[citation needed]
The techniques MozJPEG uses to achieve high compression include optimisingHuffman trees, using progressive coding to optimally split the spectrum of DCT coefficients into separate scans, and through the use oftrellis quantisation. Additionally, the presets are aggressively tuned towards the minimisation of file sizes.[citation needed]
Besides libjpeg-turbo, MozJPEG also builds upon jpegcrush, aPerl script by Loren Merritt.[11][33]
| Developer(s) | |
|---|---|
| Initial release | November 14, 2020; 4 years ago (2020-11-14) |
| Stable release | |
| Website | github |
In April 2024, Google introducedJpegli, a new JPEG coding library that offers enhanced capabilities and a 35% compression ratio improvement at high quality compression settings, while the coding speed is comparable with MozJPEG.[35]
ISO/IECJoint Photography Experts Group maintains a reference software implementation for baseJPEG (ISO/IEC 10918-1 and 18477-1) andJPEG XT extensions (ISO/IEC 18477 Parts 2 and 6-9), as well as losslessJPEG-LS (ISO/IEC 14495).[36] It also includes some of the optimizations of MozJPEG. Though also named libjpeg, it is not related to the source code provided by Independent JPEG Group (IJG) and does not support proprietary extensions introduced by IJG since 2007.
The only concern was that Guido Vollbeding is not likely subscribed to this list and IJG JPEG is essentially developed by one person.
