JPEG
(Joint Photographic Experts
Group) An ISO/ITU standard for compressing still images that is becoming very popular due to its high compression
capability. Using discrete cosine transform, it provides lossy compression (you lose some data from
the original image) with ratios up to 100:1 and higher.
It depends on the image, but ratios of 10:1 to 20:1 may provide little noticeable loss. The more
the loss can be tolerated, the more the image can be compressed. Compression is achieved by dividing
the picture into tiny pixel blocks, which are halved over and over until the ratio is achieved.
JPEG is implemented in software and hardware, with the latter providing sufficient speed for
realtime, on-the-fly compression. C-Cube Microsystems introduced the first JPEG chip.
JPEG++ is an extension to JPEG from Storm Technology, Mountain View, CA, that allows picture
areas to be selectable for different ratios. For example, the background could be compressed higher
than the foreground image.
JPEG uses the JPEG File Interchange Format, or JFIF. File extensions are .JPG or
.JFF. M-JPEG and MPEG are variations of JPEG used for full-motion digital video.
Copyright ©1998-2000 by Ultimate Systems, Inc. All Rights Reserved.