GIF

Graphics Interchange Format (GIF) is a bitmap based image file format. It was developed and introduced by CompuServe in 1987. GIF is one of the most popular image file formats used on the Internet today. The first version of GIF was 87a; CompuServe introduced an advanced version called 89a in 1989. The 89a version enabled the storage of several images in one file, so as to create simple animations.

GIF supports up to 8 bits per pixel. This permits a single image to use a palette of an upper limit of 256 colors. These colors are based on the 24 bit RGB color range. For animated GIF files, it has a separate palette of 256 colors for each frame. These sorts of color palettes make GIF suitable for basic images with solid colors rather than color rich images. GIF images utilize the Lempel-Ziv-Welch (LZW) lossless data compression process to decrease the file size, without sacrificing image quality.

Application of the GIF file format

The GIF file format can be used to produce the following:

  • Small animations and low-resolution film clips.
  • Low color sprite data for games.
  • Straight-lined and pointed artwork such as logos.

LZW patent issue

The LZW lossless compression method was first conceptualized as a result of a collaborative effort between Jacob Ziv and Abraham Lempel. Terry Welch later on created an improved and faster version of their lossless data compression algorithms; hence the name Lempel-Ziv-Welch.

Terry Welch, who was a employee of Sperry Corporation, submitted a patent application for the LZW method in 1983, and the patent was awarded to Sperry Corporation. Sperry Corporation later on combined with Burroughs Corporation to form Unisys. As a result of the popularity of the LZW compression method, Unisys had licensing agreements setup with a large number of companies.

CompuServe had also utilized the LZW method for the GIF file format, but was unaware of the fact that Unisys was the sole owner of the LZW patent. Unisys, after a long period of time, realized CompuServe was using the LZW method and setup licensing discussions with CompuServe in 1993. They finally came to an agreement in late 1994. Post the agreement with CompuServe, Unisys affirmed that they required all key commercial on-line data services companies using the LZW compression method to license the technology from Unisys at a practical rate. These rates would not extend to non-profit GIF based applications. This generated a lot of outrage and condemnation from the software development community. However; as the LZW patents for USA, UK, France, Germany, Italy and Japan have expired between 2003 and 2004, the GIF format is now available free of cost.