A photo of a European wildcat with the compression rate decreasing and hence quality increasing, from left to right | |
Filename extension |
|
---|---|
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 |
Initial release | September 18, 1992; 26 years ago |
Type of format | |
Standard | ISO/IEC 10918, ITU-T T.81, ITU-T T.83, ITU-T T.84, ITU-T T.86 |
Website | www.jpeg.org/jpeg/ |
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) | Sep 18, 1992 | Requirements and guidelines | ||
Part 2 | ISO/IEC 10918-2:1995 | T.83 (11/94) | Nov 11, 1994 | Compliance testing | Rules and checks for software conformance (to Part 1). | |
Part 3 | ISO/IEC 10918-3:1997 | T.84 (07/96) | Jul 3, 1996 | Apr 1, 1999 | Extensions | Set of extensions to improve the Part 1, including the Still Picture Interchange File Format (SPIFF).[13] |
Part 4 | ISO/IEC 10918-4:1999 | T.86 (06/98) | Jun 18, 1998 | Jun 29, 2012 | 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 10918-5:2013 | T.871 (05/11) | May 14, 2011 | 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.[14] | |
Part 6 | ISO/IEC 10918-6:2013 | T.872 (06/12) | Jun 2012 | Application to printing systems | Specifies a subset of features and application tools for the interchange of images encoded according to the ISO/IEC 10918-1 for printing. |
Short name | Bytes | Payload | Name | Comments |
---|---|---|---|---|
SOI | 0xFF, 0xD8 | none | Start Of Image | |
SOF0 | 0xFF, 0xC0 | variable size | Start Of Frame (baseline DCT) | Indicates that this is a baseline DCT-based JPEG, and specifies the width, height, number of components, and component subsampling (e.g., 4:2:0). |
SOF2 | 0xFF, 0xC2 | variable size | Start Of Frame (progressive DCT) | Indicates that this is a progressive DCT-based JPEG, and specifies the width, height, number of components, and component subsampling (e.g., 4:2:0). |
DHT | 0xFF, 0xC4 | variable size | Define Huffman Table(s) | Specifies one or more Huffman tables. |
DQT | 0xFF, 0xDB | variable size | Define Quantization Table(s) | Specifies one or more quantization tables. |
DRI | 0xFF, 0xDD | 4 bytes | Define Restart Interval | Specifies the interval between RSTn markers, in Minimum Coded Units (MCUs). This marker is followed by two bytes indicating the fixed size so it can be treated like any other variable size segment. |
SOS | 0xFF, 0xDA | variable size | Start Of Scan | Begins a top-to-bottom scan of the image. In baseline DCT JPEG images, there is generally a single scan. Progressive DCT JPEG images usually contain multiple scans. This marker specifies which slice of data it will contain, and is immediately followed by entropy-coded data. |
RSTn | 0xFF, 0xDn (n=0..7) | none | Restart | Inserted every r macroblocks, where r is the restart interval set by a DRI marker. Not used if there was no DRI marker. The low three bits of the marker code cycle in value from 0 to 7. |
APPn | 0xFF, 0xEn | variable size | Application-specific | For example, an Exif JPEG file uses an APP1 marker to store metadata, laid out in a structure based closely on TIFF. |
COM | 0xFF, 0xFE | variable size | Comment | Contains a text comment. |
EOI | 0xFF, 0xD9 | none | End Of Image |
−26 | |||||||
−3 | 0 | ||||||
−3 | −2 | −6 | |||||
2 | −4 | 1 | −3 | ||||
1 | 1 | 5 | 1 | 2 | |||
−1 | 1 | −1 | 2 | 0 | 0 | ||
0 | 0 | 0 | −1 | −1 | 0 | 0 | |
0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 |
0 | 0 | 0 | 0 | 0 | 0 | 0 | |
0 | 0 | 0 | 0 | 0 | 0 | ||
0 | 0 | 0 | 0 | 0 | |||
0 | 0 | 0 | 0 | ||||
0 | 0 | 0 | |||||
0 | 0 | ||||||
0 |
Symbol 1 | Symbol 2 |
---|---|
(RUNLENGTH, SIZE) | (AMPLITUDE) |
Illustration of edge busyness[25] |
Image | Lossless compression | Lossy compression |
---|---|---|
Original | ||
Processed by Canny edge detector |
Image | Quality | Size (bytes) | Compression ratio | Comment |
---|---|---|---|---|
Highest quality (Q = 100) | 81,447 | 2.7:1 | Extremely minor artifacts | |
High quality (Q = 50) | 14,679 | 15:1 | Initial signs of subimage artifacts | |
Medium quality (Q = 25) | 9,407 | 23:1 | Stronger artifacts; loss of high frequency information | |
Low quality (Q = 10) | 4,787 | 46:1 | Severe high frequency loss leads to obvious artifacts on subimage boundaries ('macroblocking') | |
Lowest quality (Q = 1) | 1,523 | 144:1 | Extreme loss of color and detail; the leaves are nearly unrecognizable. |
Wikimedia Commons has media related to JPEG compression. |
The JPEG still-image-compression levels, even with the large range of 5:1 to 120:1 in this study, yielded equally high levels of acceptability