JPEG
| JPEG | |
|---|---|
 | |
 A photo of a European wildcat with the compression rate, and associated losses, decreasing from left to right | |
| Filename extension | .jpg, .jpeg, .jpe.jif, .jfif, .jfi |
| Internet media type |
image/jpeg |
| Type code | JPEG |
| Uniform Type Identifier (UTI) | public.jpeg |
| Magic number | ff d8 ff |
| Developed by | Joint Photographic Experts Group, IBM, Mitsubishi Electric, AT&T, Canon Inc.[1] |
| Initial release | 18 September 1992 |
| Type of format | Lossy image compression format |
| Compression | Id |
| Extended to | JPEG 2000 |
| Standard | ISO/IEC 10918, ITU-T T.81, ITU-T T.83, ITU-T T.84, ITU-T T.86 |
| Website | jpeg |
JPEG (/ˈdʒeɪpɛɡ/ JAY-peg, short for Joint Photographic Experts Group and sometimes retroactively referred to as JPEG 1)[2][3] is a commonly used method of lossy compression for digital images, particularly for those images produced by digital photography. The degree of compression can be adjusted, allowing a selectable trade off between storage size and image quality. JPEG typically achieves 10:1 compression with a loss in image quality that, while perceptible, is widely agreed upon to be acceptable.[4] Since its introduction in 1992, JPEG has been the most widely used image compression standard in the world,[5][6] and the most widely used digital image format, with several billion JPEG images produced every day as of 2015.[7]
The Joint Photographic Experts Group created the standard in 1992,[8] based on the discrete cosine transform (DCT) algorithm.[9][10] JPEG compression is used in a number of image file formats. JPEG/Exif is the most common image format used by digital cameras and other photographic image capture devices; along with JPEG/JFIF, it is the most common format for storing and transmitting photographic images on the World Wide Web.[11] These format variations are often not distinguished and are simply called JPEG.
The MIME media type for JPEG is "image/jpeg", except in older Internet Explorer versions, which provide a MIME type of "image/pjpeg" when uploading JPEG images.[12] JPEG files usually have a filename extension of "jpg" or "jpeg". JPEG/JFIF supports a maximum image size of 65,535×65,535 pixels,[13] hence up to 4 gigapixels for an aspect ratio of 1:1. In 2000, the JPEG group introduced a format intended to be a successor, JPEG 2000, but it was unable to replace the original JPEG as the dominant image standard.[14]
History
[edit]Background
[edit]The original JPEG specification published in 1992 implements processes from various earlier research papers and patents cited by the CCITT (now ITU-T) and Joint Photographic Experts Group.[1]
The basis for JPEG's lossy compression algorithm is the discrete cosine transform (DCT),[9][10] which was first proposed by Nasir Ahmed as an image compression technique in 1972.[15][10] Ahmed published the DCT algorithm with T. Natarajan and K. R. Rao in a 1974 paper,[16] which is cited in the JPEG specification.[9]
The JPEG specification cites patents from several companies. The following patents provided the basis for its arithmetic coding algorithm.[1]
- IBM
- U.S. patent 4,652,856 – 4 February 1986 – Kottappuram M. A. Mohiuddin and Jorma J. Rissanen – Multiplication-free multi-alphabet arithmetic code
- U.S. patent 4,905,297 – 27 February 1990 – G. Langdon, J. L. Mitchell, W. B. Pennebaker, and Jorma J. Rissanen – Arithmetic coding encoder and decoder system
- U.S. patent 4,935,882 – 19 June 1990 – W. B. Pennebaker and J. L. Mitchell – Probability adaptation for arithmetic coders
- Mitsubishi Electric
- JP H02202267 (1021672) – 21 January 1989 – Toshihiro Kimura, Shigenori Kino, Fumitaka Ono, Masayuki Yoshida – Coding system
- JP H03247123 (2-46275) – 26 February 1990 – Tomohiro Kimura, Shigenori Kino, Fumitaka Ono, and Masayuki Yoshida – Coding apparatus and coding method
The JPEG specification also cites three other patents from IBM. Other companies cited as patent holders include AT&T (two patents) and Canon Inc.[1] Absent from the list is U.S. patent 4,698,672, filed by