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What's the difference between graphic and picture file formats? You've seen them-TIFF, GIF, PNG, JPEG, and BMP are among the most popular formats. In this issue, IT World surveys these file formats by looking into the history, how and where they're used, and what each one is most suited for. The story of digital picture formats is one of compression, true color, and protest campaigns. Read on!
TIFF
Tag Image File Format (TIFF) was developed in the mid-80s by the Aldus Corporation. The original intent was to be as flexible as possible when exchanging image data between machines and applications. The current specification for TIFF, created in 1992, is controlled by Adobe (version 6.0) and can be found at http://partners.adobe.com/public/developer/tiff/index.html. TIFF is popular for high color depth pictures and line art. TIFF is also supported by all the major graphics and image manipulation and desktop publishing applications as well as word processing and scanning programs.
TIFF started out as a common format for desktop scanner companies. Originally a simple bi-level image format (black and white), since that was all the scanners of the day could handle, TIFF evolved first into grayscale and then into color.
TIFF is flexible and adaptable. A single file can contain multiple images and data via tags in the file header. Tags include basic image sizing information as well as any compression means that were implemented. A TIFF file can also contain JPEG compressed images. One of the best things about TIFF is that it contains all the original data, even if edited. This is known as lossless.
TIFF also can use lossless data compression techniques like LZW. LZW comes from the authors' names-Lempel-Ziv-Welch. Actually it is Terry Welch's improved implementation of Abraham Lempel's and Jacob Ziv's LZ78 program, first launched in 1978. It was meant to be quickly implemented and therefore suffers a little bit from not being overly thorough. The LZW process, also used by GIF files, builds an ordered sequence of symbols or codes (called a string) from the data being compressed. It then takes two characters from the string and enters them as a concatenation relative to the first character of the short string. In effect we can reduce the number of bits in the file by...