Abstract: A display device with improved color and grey scale capability employs an improved time dependent dithering technique. In the display device, each pixel is controlled so as to be illuminated only a certain number of times during a fixed display time period, the number of illuminations during the time period being dependent on the color or grey scale value of a corresponding pixel in an original image, the frame number, and a dither matrix element. Additionally, the device chooses the particular frames during which a pixel is illuminated so as to give a soft and smooth displayed image with no flashing.

Abstract: A window clipping method and device for processing data with arbitrarily shaped clipping windows, wherein arbitrarily shaped clipping windows and graphic data are stored in separate bit mapped memories, employing a graphic processor and a controller. The drawing graph is drawn only inside the clipping window, and patterns of the clipping window can also be mixed with the graph. Intersection calculations of the drawing graph and the boundary of the clipping window are not employed.

Abstract: A raster video display system utilizes memory capacity more efficiently than conventional raster display systems and is independent of the specific resolution of the screen which is utilized in the system. The raster display system comprises a VRAM with split transfer capability and a unique address generator which can determine when pixels from a particular row of the screen display start on one row of the VRAM and extend over to the next row of the VRAM.

Abstract: A display control unit for combining first video signal transmitted from a first video information source which is controlled by a first pixel clock and a first synchronizing signal with second video signal transmitted from a second video information source which is controlled by a second pixel clock and a second synchronizing signal so that the first and the second video signals can be displayed on a CRT display device which is controlled by the first pixel clock and the first synchronizing signal.