The JPEG Standard
The name "JPEG" stands for Joint Photographic Experts Group, the name of the committee that created the JPEG standard and also other still picture coding standards. The "Joint" stood for ISO TC97 WG8 and CCITT SGVIII. In 1987 ISO TC 97 became ISO/IEC JTC1 and in 1992 CCITT became ITU-T. Currently on the JTC1 side JPEG is one of two sub-groups of ISO/IEC Joint Technical Committee 1, Subcommittee 29, Working Group 1 (ISO/IEC JTC 1/SC 29/WG 1) – titled as Coding of still pictures. On the ITU-T side ITU-T SG16 is the respective body. The original JPEG group was organized in 1986, issuing the first JPEG standard in 1992, which was approved in September 1992 as ITU-T Recommendation T.81 and in 1994 as ISO/IEC 10918-1.
The JPEG standard specifies the codec, which defines how an image is compressed into a stream of bytes and decompressed back into an image, but not the file format used to contain that stream. The Exif and JFIF standards define the commonly used file formats for interchange of JPEG-compressed images.
JPEG standards are formally named as Information technology – Digital compression and coding of continuous-tone still images. ISO/IEC 10918 consists of the following parts:
| Part | ISO/IEC standard | ITU-T Rec. | First public release date | Latest amendment | Title | Description |
|---|---|---|---|---|---|---|
| Part 1 | ISO/IEC 10918-1:1994 | T.81 (09/92) | 1992 | Requirements and guidelines | ||
| Part 2 | ISO/IEC 10918-2:1995 | T.83 (11/94) | 1994 | Compliance testing | rules and checks for software conformance (to Part 1) | |
| Part 3 | ISO/IEC 10918-3:1997 | T.84 (07/96) | 1996 | 1999 | Extensions | set of extensions to improve the Part 1, including the SPIFF file format |
| Part 4 | ISO/IEC 10918-4:1999 | T.86 (06/98) | 1998 | Registration of JPEG profiles, SPIFF profiles, SPIFF tags, SPIFF colour spaces, APPn markers, SPIFF compression types and Registration Authorities (REGAUT) | methods for registering some of the parameters used to extend JPEG | |
| Part 5 | ISO/IEC FDIS 10918-5 | T.871 (05/11) | (under development since 2009) | JPEG File Interchange Format (JFIF) | A popular format which has been the de facto file format for images encoded by the JPEG standard. In 2009, the JPEG Committee formally established an Ad Hoc Group to standardize JFIF as JPEG Part 5. |
Ecma International TR/98 specifies the JPEG File Interchange Format (JFIF); the first edition was published in June 2009.
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