The Raster Functions in the CGI

The Raster functionality of the CGI provides the facilities to allow the client to create, store, manipulate, and display images defined as sets of pixels. Bitmaps provide the second point in the graphics pipeline (below segmentation) at which a snapshot of the graphics data, at a particular level of refinement, can be kept and manipulated. It represents a level of storage much farther down the pipeline than segmentation, at which stage many more of the indirect references implied in the functions used in the CGI have been converted to a viewable image. For example, by the time the definition of a polyline is stored in a bitmap, the information available at the CGI/client interface about the current settings of line width, etc., have been turned into instructions to set particular pixels in the bitmap.