Graphics Interchange Format
A rotating globe in GIF format. The gradient blue areas of this image transition choppily, a common artifact produced when dithering is not employed.
File extension:	.gif
MIME type:	image/gif
Type code:	GIF
Uniform Type Identifier:	com.compuserve.gif
Magic:	GIF87a/GIF89a
Developed by:	CompuServe
Type of format:	bitmap image format

An example of a GIF image. The dithering process used to overcome the format's 256-color limitation makes the image appear coarse-grained.

GIF (Graphics Interchange Format) is an 8-bit-per-pixel bitmap image format that was introduced by CompuServe in 1987 and has since come into widespread usage on the World Wide Web due to its wide support and portability. Image File history File links No higher resolution available. ... A filename extension is a suffix to the name of a computer file applied to show its format. ... Multipurpose Internet Mail Extensions (MIME) is an Internet Standard that extends the format of e-mail to support: text in character sets other than US-ASCII; non-text attachments; multi-part message bodies; and header information in non-ASCII character sets. ... A type code is a mechanism used in pre-Mac OS X versions of the Macintosh operating system to denote a files format, in a manner similar to file extensions in other operating systems. ... A Uniform Type Identifier (UTI) is a string that uniquely identifies the type of a class of items. ... In computer programming, a magic number is a constant used to identify the file or data type employed. ... CompuServe, (in full, CompuServe Information Services, or CIS), was the first major commercial online service in the United States. ... For the use of the term raster in radio regulation, see frequency raster. ... See also Category:Graphics file formats Here is a summary of the most common graphics file formats: Some file formats, e. ... Image File history File links Size of this preview: 505 × 599 pixelsFull resolution (1160 × 1376 pixel, file size: 955 KB, MIME type: image/gif) File history Legend: (cur) = this is the current file, (del) = delete this old version, (rev) = revert to this old version. ... Image File history File links Size of this preview: 505 × 599 pixelsFull resolution (1160 × 1376 pixel, file size: 955 KB, MIME type: image/gif) File history Legend: (cur) = this is the current file, (del) = delete this old version, (rev) = revert to this old version. ... 8-bit colour graphics is a method of storing image information in a computers memory or in an image file, such that each pixel is represented by one 8-bit byte. ... Suppose the smiley face in the top left corner is an RGB bitmap image. ... See also Category:Graphics file formats Here is a summary of the most common graphics file formats: Some file formats, e. ... CompuServe, (in full, CompuServe Information Services, or CIS), was the first major commercial online service in the United States. ... Year 1987 (MCMLXXXVII) was a common year starting on Thursday (link displays 1987 Gregorian calendar). ... WWWs historical logo designed by Robert Cailliau The World Wide Web is a system of interlinked, hypertext documents accessed via the Internet. ...

The format uses a palette of up to 256 distinct colors from the 24-bit RGB color space. It also supports animations and allows a separate palette of 256 colors for each frame. The color limitation makes the GIF format unsuitable for reproducing color photographs and other images with continuous color, but it is well-suited for more simple images such as graphics or logos with solid areas of color.

GIF images are compressed using the LZW lossless data compression technique to reduce the file size without degrading the visual quality. This compression technique was patented in 1985. The controversy over the patent licensing agreement between the patent proprietor, Unisys, and CompuServe in 1994 led to the development of the PNG (Portable Network Graphics) standard. LZW (Lempel-Ziv-Welch) is an implementation of a lossless data compression algorithm created by Abraham Lempel and Jacob Ziv. ... Lossless data compression is a class of data compression algorithms that allows the exact original data to be reconstructed from the compressed data. ... Unisys Corporation (NYSE: UIS), based in Blue Bell, Pennsylvania, United States, and incorporated in Delaware[2], is a global provider of information technology services and solutions. ... PNG (Portable Network Graphics) is a bitmapped image format that employs lossless data compression. ...

History

CompuServe introduced the GIF format in 1987 to provide a color image format for their file downloading areas, replacing their earlier RLE format, which was black and white only. GIF became popular because it used LZW data compression, which was more efficient than the run-length encoding that formats such as PCX and MacPaint used, and fairly large images could therefore be downloaded in a reasonable amount of time, even with very slow modems. CompuServe, (in full, CompuServe Information Services, or CIS), was the first major commercial online service in the United States. ... Year 1987 (MCMLXXXVII) was a common year starting on Thursday (link displays 1987 Gregorian calendar). ... Run-length encoding (RLE) is a very simple form of data compression in which runs of data (that is, sequences in which the same data value occurs in many consecutive data elements) are stored as a single data value and count, rather than as the original run. ... LZW (Lempel-Ziv-Welch) is an implementation of a lossless data compression algorithm created by Abraham Lempel and Jacob Ziv. ... In computer science and information theory, data compression or source coding is the process of encoding information using fewer bits (or other information-bearing units) than an unencoded representation would use through use of specific encoding schemes. ... Run-length encoding (RLE) is a very simple form of data compression in which runs of data (that is, sequences in which the same data value occurs in many consecutive data elements) are stored as a single data value and count, rather than as the original run. ... PCX is an image file format that uses a simple form of run-length encoding (a type of lossless compression algorithm). ... MacPaint is a bitmap-based image editing computer program that was produced by Apple Computer for bundling with their Macintosh personal computer. ... A modem (from modulate and demodulate) is a device that modulates an analog carrier signal to encode digital information, and also demodulates such a carrier signal to decode the transmitted information. ...

The original version of the GIF format was called 87a. In 1989, CompuServe devised an enhanced version, called 89a,^[1] that added support for multiple images in a stream, interlacing and storage of application-specific metadata. The two versions can be distinguished by looking at the first six bytes of the file, which, when interpreted as ASCII, read "GIF87a" and "GIF89a", respectively. Year 1989 (MCMLXXXIX) was a common year starting on Sunday (link displays 1989 Gregorian calendar). ... In computer science a byte is a unit of measurement of information storage, most often consisting of eight bits. ... Image:ASCII fullsvg There are 95 printable ASCII characters, numbered 32 to 126. ...

When the World Wide Web gained popularity, GIF became one of the two image formats commonly used on Web sites, the other being the black and white XBM.^{[citation needed]} JPEG came later with the Mosaic browser. XBM (X BitMap) is an ASCII monochrome image format used by the X Window System and is used for storing cursor and icon bitmaps that are used in the X GUI. XBM files are quite different from most image files in that they are actually C language source files that... In computing, JPEG (pronounced JAY-peg; IPA: ) is a commonly used standard method of compression for photographic images. ... Mosaic is a web browser (client) for the World Wide Web written at the National Center for Supercomputing Applications (NCSA). ...

The GIF89a feature of storing multiple images in one file, accompanied by control data, is used extensively on the web to produce simple animations. The optional interlacing feature, which stored image scan lines out of order in such a fashion that even a partially downloaded image was somewhat recognizable, also helped GIF's popularity,^{[citation needed]} as a user could abort the download if it was not what was required. Computer animation is the art of creating moving images via the use of computers. ...

Pronunciation

The creators of the format pronounce GIF with a soft "g", IPA: [dʒiː], as in "George". According to the creator of the GIF format, Steve Wilhite, the pronunciation deliberately echoes that of an American peanut butter brand, Jif, and the employees of CompuServe would often say "Choosy developers choose GIF", spoofing this brand's television commercials.^{[citation needed]} This pronunciation was also identified by CompuServe in their documentation of a graphics display program called CompuShow.^[2] Many people pronounce the name with a hard "g" (as in "Graphics"),^[3] and both pronunciations are given as correct by the Oxford English Dictionary^[4] and the American Heritage Dictionary.^[5] The letter G is the seventh letter in the Latin alphabet. ... IPA may refer to: The International Phonetic Alphabet or India Pale Ale ... Steve Whilhite of CompuServe Invented the GIF Format which went on to become the de facto standard for 8-bit images on the Internet. ... Jar of creamy Jif. ... CompuServe, (in full, CompuServe Information Services, or CIS), was the first major commercial online service in the United States. ... The Oxford English Dictionary print set The Oxford English Dictionary (OED) is a dictionary published by the Oxford University Press (OUP), and is the most successful dictionary of the English language, (not to be confused with the one-volume Oxford Dictionary of English, formerly New Oxford Dictionary of English, of... The American Heritage Dictionary of the English Language (AHD) is a dictionary of American English published by Boston publisher Houghton-Mifflin, the first edition of which appeared in 1969. ...

Usage

An example of a short GIF animation made with a digital camera

• GIFs are suitable for sharp-edged line art (such as logos) with a limited number of colors. This takes advantage of the format's lossless compression which preserves very sharp edges (in contrast to JPEG).
• GIFs are used for small animations and low resolution film clips.
• In view of the limitation on the GIF formation to 256 colors, JPEG is a more commonly used format for digital photographs. JPEGs can save information on more than 16 million different colors and use more aggressive, lossy compression which has a less noticeable effect on photographs than it does on images with sharp edges.
• In circumstances where speed is more important than reduced file size, uncompressed bitmap formats such as Windows bitmap are more commonly used than the GIF format, since uncompressed bitmaps contain raw pixel information and can be displayed very quickly.
• The PNG format is becoming an increasingly popular replacement for GIF images since it uses better compression techniques and does not have a limit of 256 colors. PNGs do not support animations, however.

Image File history File links BananaShoeShine. ... Image File history File links BananaShoeShine. ... In computing, JPEG (pronounced JAY-peg; IPA: ) is a commonly used standard method of compression for photographic images. ... 10 MP Nikon D200 and a Nikon film scanner The Canon EOS 350D The Canon PowerShot A95 Digital photography, as opposed to film photography, uses electronic devices to record and capture the image as binary data. ... A lossy data compression method is one where compressing a file and then decompressing it retrieves a file that may well be different to the original, but is close enough to be useful in some way. ... DIB redirects here. ... PNG (Portable Network Graphics) is a bitmapped image format that employs lossless data compression. ...

Palettes

GIF is palette based: although any palette selection can be one of millions of shades, the maximum number that can be used in a frame is 256. These are stored in a "palette", a table that associates each palette selection number with a specific RGB value. The limitation to 256 colors seemed reasonable at the time of GIF's creation because few people could afford the hardware to display more. Simple graphics, line drawings, cartoons, and grey-scale photographs typically need fewer than 256 colors. In addition, one of the colors in the palette can optionally be set as fully transparent. A palette, in computer graphics, is a designated subset of the total range of colors supported by a computer graphics system. ... REDIRECT RGB color model ...

There exist ways to dither or diffuse photographs by using pixels of 2 or more different colors to approximate an in-between color, but this transformation inevitably loses some detail. The algorithms used to select the palette and to perform the dithering vary widely in output quality. Additionally, dithering significantly reduces the image's compressibility and thus works contrary to GIF's main purpose. This article or section should be merged with Dither An illustration of dithering. ... In mathematics, computing, linguistics, and related disciplines, an algorithm is a finite list of well-defined instructions for accomplishing some task that, given an initial state, will terminate in a defined end-state. ...

In the early days of graphical web browsers, graphics cards with 8-bit buffers (allowing only 256 colors) were common and it was fairly common to make GIF images using the websafe palette which was based on the common subset of the standard Windows and Macintosh palettes.^{[citation needed]} This ensured predictable display but severely limited the choice of colors. Now that 24-bit graphics cards are the norm, optimized palettes make less sense when creating images, though there are still many sites on web design that advise the use of the web safe palette.^{[citation needed]} Web colors are colors used in designing web pages, and the methods for describing and specifying those colors. ...

True color

Although the standard GIF format is limited to 256 colors, there is a hack^[6] that can overcome this limitation under certain circumstances. A hack in progress in Lobby 7 at MIT. Hack is a term in the slang of the technology culture which has come into existence over the past few decades. ...

GIF89a was designed based on the principle of rendering images (known as frames when used for animation) to a logical screen. Each image could optionally have its own palette, and the format provides flags to specify delay and waiting for user input between them (the latter is not widely supported by viewers). This is the feature that is used to create animated GIFs, but it can also be used to losslessly store a 24-bit RGB (truecolor) image by splitting it up into pieces small enough to be encoded into a 256 color palette and setting up the GIF to render these with no delay on the logical screen.^[7][8] However, most web browsers seem to assume that this multi-image feature will only be used for animation and insert a minimum delay between images. There will also be some file size bloat from doing this. There are few tools around that can easily produce 24-bit GIFs (e.g. ANGIF or SView5) - however it is rarely an appropriate format unless there is absolutely no other option. Truecolor (also spelled Truecolour; called Millions on a Macintosh) graphics is a method of storing image information in a computers memory such that each pixel is represented by three or more bytes. ...

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". In 1983, Terry Welch developed a fast variant of LZ78 which was named LZW.^[9][10] Jacob Ziv, along with Abraham Lempel, developed the lossless LZ77 compression algorithm. ... Abraham Lempel is a computer scientist and one of the fathers of the LZ family of lossless data compression algorithms. ... LZ77 and LZ78 are the names for the two lossless data compression algorithms published in papers by Abraham Lempel and Jacob Ziv in 1977 and 1978. ... LZ77 and LZ78 are the names for the two lossless data compression algorithms published in papers by Abraham Lempel and Jacob Ziv in 1977 and 1978. ... Terry Welch, along with Abraham Lempel and Jacob Ziv, developed the lossless LZW compression algorithm which was published in 1984. ... LZW (Lempel-Ziv-Welch) is an implementation of a lossless data compression algorithm created by Abraham Lempel and Jacob Ziv. ...

Welch filed a patent application for the LZW method in June 1983. The resulting patent, US patent 4558302, granted in December 1985, was assigned to Sperry Corporation who subsequently merged with Burroughs Corporation in 1986 and formed Unisys.^[9] Further patents were obtained in the United Kingdom, France, Germany, Italy, Japan and Canada. Sperry Corporation was a major American equipment and electronics company whose existence spanned more than seven decades of the twentieth century. ... William Seward Burroughs (1857-1898), US inventor William S. Burroughs (1914-1997), author and grandson of William Seward Burroughs Edgar Rice Burroughs (1875-1950), American author of Tarzan fame The Burroughs Corporation began in 1886 as the American Arithmometer Company in St. ... Unisys Corporation (NYSE: UIS), based in Blue Bell, Pennsylvania, United States, and incorporated in Delaware[2], is a global provider of information technology services and solutions. ...

In June 1984, an article by Welch was published in the IEEE magazine which publicly described the LZW technique for the first time.^[11] LZW became a popular data compression technique and, when the patent was granted, Unisys entered into licensing agreements with over a hundred companies.^[9][12] The Institute of Electrical and Electronics Engineers or IEEE (pronounced as eye-triple-ee) is an international non-profit, professional organization incorporated in the State of New York, United States. ...

The popularity of LZW led CompuServe to choose it as the compression technique for their GIF format, developed in 1987. At the time, CompuServe were not aware of the patent.^[9] Unisys became aware that the GIF format used the LZW compression technique and entered into licensing negotiations with CompuServe in January 1993. The subsequent agreement was announced on December 24, 1994.^[10] Unisys stated that they expected all major commercial on-line information services companies employing the LZW patent to license the technology from Unisys at a reasonable rate, but that they would not require licensing, or fees to be paid, for non-commercial, non-profit GIF-based applications, including those for use on the on-line services.^[12] CompuServe, (in full, CompuServe Information Services, or CIS), was the first major commercial online service in the United States. ... is the 358th day of the year (359th in leap years) in the Gregorian calendar. ... Year 1994 (MCMXCIV) was a common year starting on Saturday (link will display full 1994 Gregorian calendar). ...

Following this announcement, there was widespread condemnation of CompuServe and Unisys, and many software developers threatened to stop using the GIF format. The PNG format was developed in 1995 as an intended replacement.^[9][10][11] However, obtaining support from the makers of Web browsers and other software for the PNG format proved difficult and it was not possible to replace the GIF format entirely, although PNG has gradually improved in popularity.^[9] PNG (Portable Network Graphics) is a bitmapped image format that employs lossless data compression. ...

In August 1999, Unisys changed the details of their licensing practice, announcing the option for owners of Billboard and Intra net Web sites to obtain licenses on payment of a one-time license fee of $5000 or $7500.^[13] Such licenses were not required for website owners or other GIF users who had used licensed software to generate GIFs. Nevertheless, Unisys was the subject of thousands of online attacks and abusive emails from users believing that they were going to be charged $5000 or sued for using GIFs on their websites.^[14]. 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 vilified by individuals and organizations such as the League for Programming Freedom who started the "Burn All GIFs" campaign^[15] League for Programming Freedom (LPF) was founded in 1989 by Richard Stallman to unite free software developers as well as developers of proprietary software to fight against software patents and the extension of the scope of copyright. ...

The US LZW patent expired on June 20, 2003. The counterpart patents in the United Kingdom, France, Germany and Italy expired on June 18, 2004, the Japanese counterpart patents expired on June 20, 2004 and the counterpart Canadian patent expired on July 7, 2004.^[16] Consequently, while Unisys has further patents and patent applications relating to improvements to the LZW technique,^[16] the GIF format may now be used freely. is the 171st day of the year (172nd in leap years) in the Gregorian calendar. ... 2003 (MMIII) was a common year starting on Wednesday of the Gregorian calendar. ... is the 169th day of the year (170th in leap years) in the Gregorian calendar. ... shelby was here 2004 (MMIV) was a leap year starting on Thursday of the Gregorian calendar. ... is the 171st day of the year (172nd in leap years) in the Gregorian calendar. ... shelby was here 2004 (MMIV) was a leap year starting on Thursday of the Gregorian calendar. ... is the 188th day of the year (189th in leap years) in the Gregorian calendar. ... shelby was here 2004 (MMIV) was a leap year starting on Thursday of the Gregorian calendar. ...

Alternatives

PNG was designed as a replacement for the GIF format in order to avoid infringement of Unisys' patent on the LZW compression technique.^[9] PNG offers better compression and more features than GIF. The format is more suitable than GIF in instances where true-color imaging, alpha transparency, or a lossless data format are required. However, PNG does not support animation, so the GIF format is still used for simple animations. PNG (Portable Network Graphics) is a bitmapped image format that employs lossless data compression. ... LZW (Lempel-Ziv-Welch) is an implementation of a lossless data compression algorithm created by Abraham Lempel and Jacob Ziv. ... In computer graphics, alpha compositing is often useful to render image elements in separate passes, and then combine the resulting multiple 2D images into a single, final image in a process called compositing. ...

Although it took time for the PNG format to be supported, new web browsers support the PNG format and GIF images can usually be replaced by PNG images if desired. However, Internet Explorer versions 6 and earlier do not support PNG's alpha channel transparency feature without using Microsoft-specific HTML extensions.^[17] Using standard HTML <img> tags for PNG images in Internet Explorer can produce a look different from that intended. Internet Explorer 7 supports alpha channel transparency without needing extensions.^[18] An example of a web browser (Internet Explorer), displaying the English Wikipedia main page. ... Windows Internet Explorer (formerly Microsoft Internet Explorer, abbreviated MSIE), and commonly abbreviated to IE, is a series of proprietary graphical web browsers developed by Microsoft and included as part of the Microsoft Windows line of operating systems starting in 1995. ... In computer graphics, alpha compositing is often useful to render image elements in separate passes, and then combine the resulting multiple 2D images into a single, final image in a process called compositing. ...

There have been claims that PNG files are generally larger than GIFs.^{[citation needed]} PNG files can indeed be much larger than GIF files in situations where a GIF and a PNG file were created from a high-quality master image, as PNG is capable of storing more color depth and transparency information than GIF. However, identical 8-bit (or lower) image data rendered in PNG and GIF formats should yield similar sizes. Misinformation about PNG efficiency can generally be traced back to poor PNG support in older versions of some image manipulation programs, (for example Adobe Photoshop did not optimize PNGs for reduced color palettes by default).^{[citation needed]} “Photoshop” redirects here. ...

MNG, a variant of PNG that supports animation, reached version 1.0 in 2001, but few applications support it. Animated GIF remains widely used as many applications are capable of creating the files, and it remains the only animated image format capable of being rendered in nearly all modern web browsers without the use of a plug-in.^{[citation needed]} Nevertheless, embedded Flash objects, MPEGs and other video formats are used in place of animated GIFs in many websites. Other approaches, such as individual frames served by AJAX, or SVG images may be animated via JavaScript. In 2004, a proposed extension to the PNG format called APNG was suggested. It was to provide the ability to animate PNG files, while retaining backwards compatibility in decoders that cannot understand the animation chunk. Older decoders would simply render the first frame of the animation. Multiple-image Network Graphics (MNG) (IPA pronunciation: ) is a public graphics file format for animated images. ... Year 2001 (MMI) was a common year starting on Monday (link displays the 2001 Gregorian calendar). ... // Ajax (mythology), also known as Telamonian Ajax or Ajax the Great, a Greek hero and legendary king of Salamis who plays an important role in Homers Iliad Ajax the Lesser, or Oilean Ajax, a Greek hero and legendary king of Locris who appears in Homers Iliad Ajax (Sophocles... SVG is also the IATA code for Stavanger Airport, Sola in Norway. ... shelby was here 2004 (MMIV) was a leap year starting on Thursday of the Gregorian calendar. ... The APNG (Animated Portable Network Graphics) file format is an extension to the Portable Network Graphics (PNG) specification proposed by Stuart Parmenter and Vladimir Vukicevic of the Mozilla Corporation. ...

See also

• Comparison of graphics file formats
• Comparison of layout engines (graphics)
• Image file formats
• JPEG
• PNG
• Software patent
• Windows Picture and Fax Viewer

It has been suggested that Graphics file format summary be merged into this article or section. ... The following tables compare graphics compatibility and support for a number of layout engines. ... Image file formats provide a standardized method of organizing and storing image data. ... In computing, JPEG (pronounced JAY-peg; IPA: ) is a commonly used standard method of compression for photographic images. ... PNG (Portable Network Graphics) is a bitmapped image format that employs lossless data compression. ... Software patent does not have a universally accepted definition. ... Windows Picture and Fax Viewer is an image viewer. ...

References

CompuServe, (in full, CompuServe Information Services, or CIS), was the first major commercial online service in the United States. ... Year 2007 (MMVII) is now the current year, a common year starting on Monday of the Gregorian calendar and the AD/CE era. ... is the 105th day of the year (106th in leap years) in the Gregorian calendar. ... Year 2007 (MMVII) is now the current year, a common year starting on Monday of the Gregorian calendar and the AD/CE era. ... is the 105th day of the year (106th in leap years) in the Gregorian calendar. ... League for Programming Freedom (LPF) was founded in 1989 by Richard Stallman to unite free software developers as well as developers of proprietary software to fight against software patents and the extension of the scope of copyright. ... Slashdot, often abbreviated as /., is a science, science fiction, and technology-related news website owned by SourceForge, Inc. ...

External links

• GIF89a specification
• GIF Animation on the WWW - technical explanation of the GIF89a format and how it allows animation
• LZW GIF decoding by Arturo San Emeterio Campos
• LZW and GIF explained
• Replacing a Dictionary with a Square Root - suggestions for compressing GIFs without using LZW compression
• Web Graphics discusses and illustrates the differences between GIF, JPEG and PNG formats