Vector graphics Representation of an image in terms of lines and shapes 3.6 Representing Images and Graphics 77 pixel color values of the image from left to right and top to bottom. A bitmap file supports 24-bit TrueColor, though usually the color depth can be specified to reduce the file size. A bitmap file may be compressed using run-length encoding as described earlier in this chapter. The GIF format (Graphics Interchange Format), developed by CompuServe in 1987, uses indexed color exclusively to reduce file size, which limits the number of available colors to 256. If even fewer colors are required, the color depth can usually be specified to fewer bits. GIF files are best used for graphics and images with few colors, and are therefore considered optimal for line art. The JPEG format is designed to exploit the nature of our eyes. Humans are more sensitive to gradual changes of brightness and color over distance than we are to rapid changes. Therefore, the data that the JPEG format stores averages out the color hues over short distances. The JPEG format is
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