Raster-Scan Display Processor

Figure shows one way to organize the components of a raster system that contains a separate display processor, sometimes referred to as a graphics controller or a display coprocessor.

Scan conversion:

• A major task of the display processor is digitizing a picture definition given in an application program into a set of pixel values for storage in the frame buffer.
•  This digitization process is called scan conversion.

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Example 1:

displaying a line

•  Graphics commands specifying straight lines and other geometric objects are scan converted into a set of discrete points, corresponding to screen pixel positions.
• Scan converting a straight-line segment.

Example 2:

displaying a character

•  Characters can be defined with rectangular pixel grids
• The array size for character grids can vary from about 5 by 7 to 9 by 12 or more for higher-quality displays.
• A character grid is displayed by superimposing the rectangular grid pattern into the frame buffer at a specified coordinate position