JPS6421684A - Shade adding device for image - Google Patents

Abstract

PURPOSE:To successively execute an adding to the luminance of the starting point of a scan line and to obtain the luminance data of respective picture elements with a small memory capacity by preparing the luminance data, in which a value to have various inclinations of the luminance changes in a straight line-shape, as one group per inclination to a memory and reading the luminance data of the straight line change of the inclination from this memory in correspondence to the respective picture elements of the scan line. CONSTITUTION:To a memory 11 of the shade adding device of an image, the X coordinate of the starting and ending points of the respective scan lines of a polygon from a scan line converting circuit 2 and the luminance data of the starting point are written per line by the control of a controller 10. Simultaneously, the data of the inclination of the scan line from a luminance inclination operating circuit 3 are written. The luminance data are stored to a memory 12 of approximate luminance data in a picture element bit to correspond to the various inclinations of the luminance change. Then, the controller 10 is operated at a timing to display the read data to a CRT 14 and luminance information and approximate straight line information from memories 11 and 12 on a line are successively added by a D/A 13 with adding function.