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Image transformations on an interactive raster scan or matrix display

  • US 4,688,181 A
  • Filed: 04/30/1986
  • Issued: 08/18/1987
  • Est. Priority Date: 12/22/1982
  • Status: Expired due to Term
First Claim
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1. An interactive raster-scanned display system including a microprocessor and random-access store operable to issue control signals to a drawing engine in order to display a full image on a display screen, said engine being arranged in operation in image transformation mode repetitively to erase and redraw such an image so as to change its position and/or shape in response to real-time commands received by said microprocessor from an interactive input device, characterized in that, in order to reduce the demands imposed on the drawing engine during real-time image transformation, control means are provided in said system arranged in operation in image transformation mode to substitute for said full image required to be transformed, an alternative image representing said full image but containing less detail to be drawn, and on completion of said tranformation to replace said alternative image by said full image,in which said control means is arranged in operation to, by and substantially upon receipt of a first command from said input device, invoke image transformation means to cause said engine to erase the full image to be transformed currently on display and thereupon to draw, incrementally transformed as required by said first command, said alternative image, said control means being further arranged in operation to, in response to receipt of subsequent commands, cause said engine repetitively to erase and redraw the alternative image with incremental transformation as required in turn by each of said subsequent commands, andin which means are provided to form in an input queue said transformation commands from said input device and to process the queued commands in order of arrival by said microprocessor, said control means being operable by and substantially upon receipt of a subsequent transformation command before the current drawing operation of the alternative image is complete to cause said engine to erase the partially drawn alternative image and to redraw said alternative image transformed as required by the most recently received command in said queue.

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