1.5. Coding of graphic information

There are several ways to encode graphic information.

When considering a black and white graphic image using a magnifying glass, it is noticeable that it includes several tiny dots that form a characteristic pattern (or a raster). Linear coordinates and individual properties of each of the image points can be expressed with the help of integers, therefore the method of raster coding is based on the use of the binary code of representation of graphic data. The well-known standard is considered to bring black and white illustrations in the form of a combination of dots with 256 gradations of gray, that is, 8-bit binary numbers are needed to encode the brightness of any point.

The basis for coding color graphics is the principle of decomposition of an arbitrary color into main components, in which three primary colors are used: red (Red), green (Green) and blue (Blue). In practice, it is assumed that any color that the human eye perceives can be obtained by using a mechanical combination of these three colors. This coding system is called RGB (after the first letters of the primary colors). When 24 bits are used to encode color graphics, this mode is called full color (true color).

Each of the primary colors is matched with a color that complements the base color to white. For any of the primary colors, a color that is formed by the sum of a pair of other primary colors will be optional. Accordingly, among the additional colors can be distinguished cyan (Cyan), Magenta (Magenta) and yellow (Yellow). The principle of decomposition of an arbitrary color into components is used not only for primary colors, but also for additional ones, that is, any color can be represented as a sum of cyan, magenta, and yellow. This color coding method is used in printing, but there is also used the fourth paint - black (Black), so this coding system is indicated by four letters - CMYK. To represent color graphics in this system, 32 binary digits are used. This mode is also called full color.

By reducing the number of binary bits used to encode the color of each point, the amount of data is reduced, but the range of coded colors is noticeably reduced. Color graphics coding with 16-bit binary numbers is called High Color mode. When coding graphic color information using 8 data bits, only 256 shades can be transmitted. This color coding method is called index color .