| 摘要 |
A raster scan display apparatus for generating both graphic and textual images. The display refresh memory (46) is broken into an information memory (79) and an attribute memory (120). The information memory has one location for each picture element in the display; the attribute memory is of lower resolution and has one memory location for a plurality of picture elements. The attribute memory provides foreground and background attributes which can be varied only in multiples of picture element locations. In response to the information memory contents for each location, either the foreground or the background attribute is provided to the display, from the attribute memory. The information and attribute memories operate in conjunction with a pattern generator (136, 160, 162) to establish the information to be displayed between pairs of points. The pattern generator provides a finite length, repeating pattern of 1's and 0's representing the selection of foreground or background attribute for each location intermediate first and second points on the display. The rate at which the pattern is shifted may be varied to alter character or object size on the display, thus permitting all sizes of a character to be represented in memory in a cell of small fixed size. For generating two-dimensional images, two pattern generators are employed; the second pattern generator provides the starting positions and patterns for the first pattern generator. This permits characters to be reoriented-i.e., tilted, italicized, etc., with simple commands which reset the parameters governing the operation of the pattern generators. |
