Rather than break the data into formal sub-blocks, the extension block terminates with a "magic trailer" that routes any application treating the data as sub-blocks to a final 0 byte that terminates the sub-block chain. == Unisys and LZW patent enforcement == In 1977 and 1978, Jacob Ziv and Abraham Lempel published a pair of papers on a new class of lossless data-compression algorithms, now collectively referred to as LZ77 and LZ78.
Rather than break the data into formal sub-blocks, the extension block terminates with a "magic trailer" that routes any application treating the data as sub-blocks to a final 0 byte that terminates the sub-block chain. == Unisys and LZW patent enforcement == In 1977 and 1978, Jacob Ziv and Abraham Lempel published a pair of papers on a new class of lossless data-compression algorithms, now collectively referred to as LZ77 and LZ78.
Further patents were obtained in the United Kingdom, France, Germany, Italy, Japan and Canada. In addition to the above patents, Welch's 1983 patent also includes citations to several other patents that influenced it, including two 1980 Japanese patents (JP9343880A and JP17790880A) from NEC's Jun Kanatsu, (1974) from John S.
Holtz, and a 1981 Dutch patent (DE19813118676) from Karl Eckhart Heinz. In June 1984, an article by Welch was published in the IEEE magazine which publicly described the LZW technique for the first time.
In 1983, Terry Welch developed a fast variant of LZ78 which was named Lempel–Ziv–Welch (LZW). Welch filed a patent application for the LZW method in June 1983.
Further patents were obtained in the United Kingdom, France, Germany, Italy, Japan and Canada. In addition to the above patents, Welch's 1983 patent also includes citations to several other patents that influenced it, including two 1980 Japanese patents (JP9343880A and JP17790880A) from NEC's Jun Kanatsu, (1974) from John S.
Holtz, and a 1981 Dutch patent (DE19813118676) from Karl Eckhart Heinz. In June 1984, an article by Welch was published in the IEEE magazine which publicly described the LZW technique for the first time.
This compression technique was patented in 1985.
The resulting patent, , granted in December 1985, was assigned to Sperry Corporation who subsequently merged with Burroughs Corporation in 1986 and formed Unisys.
The resulting patent, , granted in December 1985, was assigned to Sperry Corporation who subsequently merged with Burroughs Corporation in 1986 and formed Unisys.
The Graphics Interchange Format (GIF; or ) is a bitmap image format that was developed by a team at the online services provider CompuServe led by American computer scientist Steve Wilhite on 15 June 1987.
By 2004 all the relevant patents had expired. ==History== CompuServe introduced GIF on 15 June 1987 to provide a color image format for their file downloading areas.
By December 1987, for example, an Apple IIGS user could view pictures created on an Atari ST or Commodore 64.
LZW became a popular data compression technique and, when the patent was granted, Unisys entered into licensing agreements with over a hundred companies. The popularity of LZW led CompuServe to choose it as the compression technique for their version of GIF, developed in 1987.
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.
To enable an animation to loop, Netscape in the 1990s used the Application Extension block (intended to allow vendors to add application-specific information to the GIF file) to implement the Netscape Application Block (NAB).
Unisys became aware that the version of GIF used the LZW compression technique and entered into licensing negotiations with CompuServe in January 1993.
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.
The subsequent agreement was announced on 24 December 1994.
The PNG format (see below) was developed in 1995 as an intended replacement.
Dobb's article described another alternative to LZW compression, based on square roots. In August 1999, Unisys changed the details of their licensing practice, announcing the option for owners of certain non-commercial and private websites to obtain licenses on payment of a one-time license fee of $5000 or $7500.
Despite giving free licenses to hundreds of non-profit organizations, schools and governments, Unisys was completely unable to generate any good publicity and continued to be condemned by individuals and organizations such as the League for Programming Freedom who started the "Burn All GIFs" campaign in 1999. The United States LZW patent expired on 20 June 2003.
MNG reached version 1.0 in 2001, but few applications support it. In 2006, an extension to the PNG format called APNG ("Animated Portable Network Graphics") was proposed as alternative to the MNG format by Mozilla.
Despite giving free licenses to hundreds of non-profit organizations, schools and governments, Unisys was completely unable to generate any good publicity and continued to be condemned by individuals and organizations such as the League for Programming Freedom who started the "Burn All GIFs" campaign in 1999. The United States LZW patent expired on 20 June 2003.
By 2004 all the relevant patents had expired. ==History== CompuServe introduced GIF on 15 June 1987 to provide a color image format for their file downloading areas.
The counterpart patents in the United Kingdom, France, Germany and Italy expired on 18 June 2004, the Japanese patents expired on 20 June 2004, and the Canadian patent expired on 7 July 2004.
MNG reached version 1.0 in 2001, but few applications support it. In 2006, an extension to the PNG format called APNG ("Animated Portable Network Graphics") was proposed as alternative to the MNG format by Mozilla.
The PNG group officially rejected APNG as an official extension on 20 April 2007.
In 2012, the American wing of the Oxford University Press recognized GIF as a verb as well, meaning "to create a GIF file", as in "GIFing was the perfect medium for sharing scenes from the Summer Olympics".
On the occasion of receiving a lifetime achievement award at the 2013 Webby Award ceremony, Wilhite rejected the hard-"G" pronunciation, and his speech led to 17,000 posts on Twitter and 50 news articles.
The White House and TV program Jeopardy! also entered the debate during 2013. In February 2020, The J.M.
Notable examples are Gfycat and Imgur and their GIFV metaformat, which is really a video tag playing a looped MP4 or WebM compressed video. High Efficiency Image File Format (HEIF) is an image file format, finalized in 2015, which uses a discrete cosine transform (DCT) lossy compression algorithm based on the HEVC video format, and related to the JPEG image format.
In 2017, an informal poll on programming website Stack Overflow showed some numerical preference for hard-"G" pronunciation, especially among respondents in eastern Europe, though both soft-"G" and saying each letter individually were found to be popular in Asia and emerging countries. Dictionary.com cites both, indicating "jif" as the primary pronunciation, while Cambridge Dictionary of American English offers only the hard-"G" pronunciation.
In January 2018 Instagram also added GIF stickers to the story mode. ==Terminology== As a noun, the word GIF is found in the newer editions of many dictionaries.
APNG is supported by most browsers as of 2019.
The White House and TV program Jeopardy! also entered the debate during 2013. In February 2020, The J.M.
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