A quarter century turned GIF format
Exactly 25 years ago, on June 15, 1987, specialists from CompuServe , which is now a division of AOL, created the Graphic Interchange Format (GIF) raster image format specifically for transmission to global computer networks.
GIF format is characterized by the following properties:
Technically, the ability to create compact color images in the GIF format is based on the data compression algorithm, which was developed in 1977 by Israeli information theory specialists Jacob Ziv and Abraham Lempel; the algorithm was named LZ (Lempel-Ziv) after the first letters of the names of its creators. Later, in 1984, Terry Welch, an employee of Unisuse, improved the implementation of the Ziva-Lempel algorithm, and thus the compression method is now known as LZW (Lempel-Ziv-Welch)
Under the spoiler - GIF-animation, created by fans specifically for the anniversary.
In the global sense, the GIF format is based on a block structure — programs for reading gif files can read blocks and skip them when reading, since its size is indicated for each block. Moving blocks on the screen with sequence marks can create an animated image.
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In 1994, Unisys, which owns a patent for the LZW compression method, decided to sell licenses for its use, which cost about $ 5000 in 1995 (the patent also owned IBM, however, the company did not use it like its colleagues - it came to that that even web sites paid licenses where gifs were created dynamically). On June 20, 2003, the validity of the Unisus main patent on the LZW method in the United States expired, and patents in Europe and Canada were valid only until July 7, 2004.
A retrospective of GIFs on the anniversary can be viewed at this link .
A good Russian-language site dedicated to the GIF is here .
GIF format is characterized by the following properties:
- Image size - from 1x1 to 65535x65535 pixels.
- The number of colors of the palette is from 2 to 256.
- Each color palette has a depth of 24 bits / pixel (a choice of 16 million colors).
- Transparency map - 1-bit (no translucent colors).
- The number of repetitions of animation - from 1 to 65535, as well as infinite.
- The time for displaying one frame of animation is from 1/100 of a second to 655 seconds.
- The number of frames of animation is unlimited.
- The number of invisible text comments and the size of each comment is unlimited.
Technically, the ability to create compact color images in the GIF format is based on the data compression algorithm, which was developed in 1977 by Israeli information theory specialists Jacob Ziv and Abraham Lempel; the algorithm was named LZ (Lempel-Ziv) after the first letters of the names of its creators. Later, in 1984, Terry Welch, an employee of Unisuse, improved the implementation of the Ziva-Lempel algorithm, and thus the compression method is now known as LZW (Lempel-Ziv-Welch)
Under the spoiler - GIF-animation, created by fans specifically for the anniversary.
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In the global sense, the GIF format is based on a block structure — programs for reading gif files can read blocks and skip them when reading, since its size is indicated for each block. Moving blocks on the screen with sequence marks can create an animated image.
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In 1994, Unisys, which owns a patent for the LZW compression method, decided to sell licenses for its use, which cost about $ 5000 in 1995 (the patent also owned IBM, however, the company did not use it like its colleagues - it came to that that even web sites paid licenses where gifs were created dynamically). On June 20, 2003, the validity of the Unisus main patent on the LZW method in the United States expired, and patents in Europe and Canada were valid only until July 7, 2004.
A retrospective of GIFs on the anniversary can be viewed at this link .
A good Russian-language site dedicated to the GIF is here .
Source: https://habr.com/ru/post/145906/
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