GIF (Graphics Interchange Format)

The CompuServe Graphics Interchange Format (GIF) is the file format commonly used to display indexed-color graphics and images in web pages on the Internet. GIF (pronounced Jif) is a compressed format that is designed to minimise file transfer time over phone lines. The GIF format discards information. GIF converts the image to Indexed color mode i.e. the number of colors is reduced to 256 - adequate for screen display but not for high quality reproduction. Unfortunately, the owners of the patent on this format let it proliferate and now try to charge royalties

Gif is compressed image file format best suited to diagrams and images with a restricted color range. In GIF compression, the color range of the image is first reduced to 256 colors or less, then the remaining information is further reduced in size by a scheme known as LZW (Lempel-Ziv-Welch) compression. LZW compression is lossless, which means that you can edit and re-save the image without degrading it, but the initial color-space compression makes the format unsuitable for high-quality color photographs. Note however, that the 256 levels in a black and white image can be indexed as colors, which means that the GIF format is ideal for high quality continuous-tone monochrome images.