JPEG.
1. Joint Photographic Experts Group. An international committee of computer imaging experts. Pronounced “jay-peg.”
2. A digital image compression algorithm defined by the organization. JPEG pictures are (usually 24-bit) images upon which lossy compression techniques have been applied in order to reduce dramatically the filesize of a picture. JPEG images are used on the Web and by many digital cameras. An important aspect of JPEG is that the standard is open and non-proprietary - anyone can use it.
Typically a JPEG picture can be 1/10 the size of an uncompressed image and still maintain reasonable picture quality. The amount of compression can be adjusted - you can optimize quality and sacrifice compression efficiency or you can go for small file sizes and sacrifice quality. The fact that JPEG is lossy is critical in another way - it’s a bad idea to repeatedly save a JPEG image to disc between alterations. Every time you save a modified JPEG you get more quality degradation. It’s rather like duplicating an audio cassette over and over.
The compression techniques used by JPEG are ideal for compressing photographs and other naturalistic images with large areas of continuous tone. They aren’t so good at compressing high-contrast images with sharp transitions or large areas of solid colour.
Note that JPEG defines a compression standard, not a file format. Technically speaking JFIF is the most common file format used by JPEG, so people should talk about JFIF files and not JPEG files. In practice, however, everybody talks about JPEG files.
Entry last updated 2002-04-03. Term 675 of 1487.
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