REALIZATION OF MULTIWINDOW SYSTEM WITH HIGH-SPEED OPERATIONS OF NONRECTANGULAR WINDOWS

This paper describes the realization of the multiwindow system, where the framed nonrectangular windows can be operated with a high speed. T he body image (the image to be displayed inside the frame) and the fra me image (the image to be displayed as the frame), which are stored on the multiport memory, are read out in parallel, being synchronized to the CRT scanning, By selecting pixelwise one of those images, the win dow image displayed in the window is generated as a framed image. The selection signal for this purpose is generated based on the window sha pe information stored in the dedicated memory. The multiwindow image i s generated by selecting the image to be displayed for each pixel posi tion on CRT using a hardware, A distributed priority encoder is used a s the hardware for this purpose. According to the result of constructi on and experiment, it is expected that the multiwindow system can real ize a sufficiently high-speed operation from the practical viewpoint f or the 1200 x 1000 CRT screen using the existing circuit technology.