Joint Photographic Experts Group

lastmod 2022-09-14created 2014-09-178 edits

JPEG (Joint Photographic Experts Group, pronounced "jay-peg") is a standard lossy compression method made for still images. The standard was established by ISO and ITU-T. File formats that use JPEG are also commonly called JPEG images and use extensions such as .jpg, .jpeg, and .jpe. Images can be stored in 16,777,216 colors or 256-level grayscale. The JPEG standard specifies only how an image is turned into a sequence of bytes. JFIF (JPEG File Interchange Format), an extension of JPEG created by the Independent JPEG Group (IJG), is an image file format that wraps a JPEG stream in a form suitable for storage and transmission. For storing photos in digital cameras, another extension, the EXIF JPEG format, is used more often. A "JPEG file" usually means the JFIF or EXIF JPEG format, but other JPEG-based file formats such as JNG also exist.

Although it is a lossy format, it is widely used on the web because of its small file size. Raising the compression ratio makes the file smaller but lowers the image quality further.

JPEG/JFIF is the most widely used file format for storing and transmitting photos and other images on the web. However, this compression method is at a disadvantage compared with GIF or PNG when converting images with many high-frequency components, such as text, lines, and fine grids, and often shows poor quality. The JPEG standard also defines a lossless compression method, but it is rarely used because of patent issues and compression ratio, and formats that support lossless compression, such as PNG, are used instead.

JPEG vs JPG

• Difference Between JPG and JPEG - KeyCDN Support

JPEG

JPEG is a file extension that stands for Joint Photographic Experts Group. The ISO standard was first released in 1992. It is a bitmap compression format most commonly used for lossy compression, with a compression ratio between 10:1 and 20:1. The compression ratio can be adjusted. That is, you can decide the trade-off between storage size and quality. The JPEG extension is most commonly used by digital cameras and photo-sharing devices.

The JPEG format is excellent for color and photos, but note that compression causes some loss of quality. And each time you edit and re-save, quality degrades, even if negligibly. One way to minimize this is to work with RAW JPEG, finalize your edits, and then save the final version without re-saving it many times.

The MIME media type for JPEG is image/jpeg (defined in RFC 1341 ). The exception is older Internet Explorer versions, which supply the MIME type image/pjpeg when uploading JPEG images. JPEG is also defined with the additional extensions , , .jpe and . .jif, .jfif, </code>.jfi</code>

JPG

Then there is the JPG format. In fact, there is no difference between the JPG and JPEG formats. The only difference is the number of characters used. JPG exists because earlier versions of Windows (MS-DOS 8.3 and the FAT-16 file system) required three-letter extensions for file names. So it was shortened to .jpeg </code>.jpg</code>. Windows and/or DOS had this limitation but UNIX did not, so UNIX and MAC users kept using the .jpeg extension. Of course, recent versions of Windows now allow more characters in file extensions. However, since .jpg was already used by most people (and by programs needed to work with MS-DOS 8.3), it is still the most common extension.

Photo editing programs such as Adobe Photoshop and Gimp all save JPEGs to the .jpg extension on Windows and MAC by default. And in case you wonder, you can change the extension either way and the file will still work.

See also

• IJPEG

Favorite site

• Wikipedia (en) Description of JPEG
• Intel IPP: Image Compression Functions ¹

References