Latest update on Thursday 16 October 2008 à 09:43 by Jean-François Pillou.
GIF format
The GIF format (Graphic Interchange Format) is a bitmap (raster) graphic file format developed by Compuserve.
There are two versions of this file format developed respectively in 1987 and 1989:
GIF 87a supporting LZW compression, interlacing (allowing progressive display), a 256 color palette and the possibility animated images (called animated GIFs) by storing several images within the same file.
GIF 89a adding the possibility of defining a transparent color to the palette and of specifying the time for animations.
Characteristics of the GIF format
A GIF image may contain between 2 and 256 colors (2, 4, 8, 16, 32, 64, 128 or 256) among 16.8 million in its palette. Thus, due to this palette with a limited number of colors (not limited in different colors), the images obtained by this format are generally very small in size.
However, given the proprietary character of the LZW compression algorithm, all software publishers handling GIF images must pay a royalty to Unisys, the company that is the holder of the rights. This is one of the reasons why the PNG format is becoming increasingly more popular, to the detriment of the GIF format.
