To facilitate contour enhancement correction, etc. for characters and graphics of another plane to be superposed on a video plane.
This image data processing circuit is provided with palette memories (20, 21, 22) to be utilized for alpha composition of a plurality of additional information planes (13, 14, 15) for performing the alpha composition of the additional information planes (13, 14, 15) to image planes (10, 1) and the palette memories can output alpha value data and color difference data in parallel based on data of corresponding additional information plane. Since the palette memories can variably output an alpha value according to the data of additional information plane, desired contour enhancement correction, etc. is enabled based on the alpha value which can be variably outputted. No exclusive correction circuit is required. Since the palette memory can output data specifying the alpha value, red, green and blue in parallel, alpha composition processing can also be performed efficiently.
FUKUOKA TETSUYA
MIYAMOTO SUNAO
TANAKA KAZUHIKO
NAKADA KEIMEI
