Patent ID: 7612911

Claim:
An image processing device for converting color image data expressed by a first color system to image data expressed by a second color system representing each pixel data as a dot on/off state for each color, the image processing device comprising: a color conversion unit that converts color image data expressed by the first color system to color image data expressed by the second color system; an edge detection unit that detects whether or not an edge exists in a first type of block into which specified adjacent pixels are grouped; a compressed data storage unit that compresses the color image data of pixels contained in the first type of block and stores the compressed color image data in a memory when the edge detection unit detects that no edge exists in the first type of block; a data decompression unit that decompresses the compressed color image data read from the memory to color image data of each pixel and groups specified adjacent pixels into a second type of block; and a dot formation judgment unit that judges in block units for each color of the second color system the dot on/off state for each pixel contained in the block based on the decompressed color image data of pixels grouped into the second type of block.