COMPRESSION SCHEME USING QUALIFIER WATERMARKING AND APPARATUS USING THE COMPRESSION SCHEME FOR TEMPORARILY STORING IMAGE DATA IN A FRAME MEMORY

摘要

Display driver (10) with a frame memory (13) for temporarily storing image data representing a color image, and a data bus (11.1) for feeding image data to the display driver (10). The display driver (10) comprises means for performing a decision process (8, 9), said decision process being based on an analysis of the color characteristics of a pixel cluster of said image data, the means for performing a decision process (8, 9) allowing the display driver (10) to decide whether a first compression format or a second compression format is to be applied for compression of said pixel cluster. It further comprises first compression means (7) performing a compression of said pixel cluster into said first compression format, and second compression means (6) performing a compression of said pixel cluster into said second format. The first compression format or second compression format is selected based upon the results of the decision process so that the compressed pixel clusters can be stored after compression in an available storage area of the frame memory (13). A compression- format code is stored indicating which compression format was used for which pixel cluster. This compression- format code is embedded into the compressed pixel clusters as a watermark.