IMAGE PROCESSING DEVICE AND IMAGE PROCESSING METHOD FOR PERFORMING CONVERSION OF COLOR IMAGE DATA

The purpose of the image processing device is to convert color image data rapidly to data expressed by the dot on/off state. A plurality of adjacent pixels is grouped as a first type of block, and judgment of the dot on/off state performed by suitably using the error diffusion method is performed in block units. The image data after the color conversion used for this judgment is stored once in memory in a compressed state according to the result of edge detection for the block, and when necessary, judgment of the dot on/off state is performed while reading from the memory. The image processing device realizes the judgment rapidly while avoiding making more complex the judgment of the dot on/off state performed in block units. Also, the image data is compressed according to the result of edge detection, so it is possible to read and write rapidly in relation to memory, and furthermore to decompress rapidly. The image processing device rapidly performs the process of color converting color image data and converting data expressed by the dot on/off state without making the processing contents more complex.