GIF was one of the first two image formats commonly used on Web sites, the other being the black-and-white XBM. By December 1987, for example, an Apple IIGS user could view pictures created on an Atari ST or Commodore 64. The two versions can be distinguished by looking at the first six bytes of the file (the " magic number" or signature), which, when interpreted as ASCII, read "GIF87a" and "GIF89a", respectively.ĬompuServe encouraged the adoption of GIF by providing downloadable conversion utilities for many computers. The 89a specification also supports incorporating text labels as text (not embedding them in the graphical data), but as there is little control over display fonts, this feature is not widely used. In 1989, CompuServe released an enhanced version, called 89a, which added support for animation delays (multiple images in a stream were already supported in 87a), transparent background colors, and storage of application-specific metadata. The original version of GIF was called 87a. Since this was more efficient than the run-length encoding used by PCX and MacPaint, fairly large images could be downloaded reasonably quickly even with slow modems. GIF became popular because it used LZW data compression. This replaced their earlier run-length encoding format, which was black and white only. By 2004, all of the relevant patents had expired.įurther information: § Unisys and LZW patent enforcementĬompuServe introduced GIF on 15 June 1987 to provide a color image format for their file downloading areas.
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Controversy over the licensing agreement between the software patent holder, Unisys, and CompuServe in 1994 spurred the development of the Portable Network Graphics (PNG) standard. This compression technique was patented in 1985. GIF images are compressed using the Lempel–Ziv–Welch (LZW) lossless data compression technique to reduce the file size without degrading the visual quality. These palette limitations make GIF less suitable for reproducing color photographs and other images with color gradients, but well-suited for simpler images such as graphics or logos with solid areas of color. It also supports animations and allows a separate palette of up to 256 colors for each frame. The format supports up to 8 bits per pixel for each image, allowing a single image to reference its own palette of up to 256 different colors chosen from the 24-bit RGB color space. It has since come into widespread usage on the World Wide Web due to its wide support and portability between applications and operating systems. The Graphics Interchange Format ( GIF / dʒ ɪ f/ JIF or / ɡ ɪ f/ GHIF, see pronunciation) is a bitmap image format that was developed by a team at the online services provider CompuServe led by American computer scientist Steve Wilhite and released on 15 June 1987.
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