A foreground pixel block extraction process section divides input image data into a plurality of pixel blocks, and classifies each pixel block as a uniform density pixel block or foreground pixel block. By performing above process, the foreground pixel block extraction process section extracts foreground pixel blocks. A foreground color calculation process section calculates the foreground colors from the extracted foreground pixel blocks as color information. A labeling process section extracts connected foreground pixel block areas as foreground pixel areas by giving the same label to a plurality of adjacent foreground pixel blocks. From these processing results, a foreground pixel extraction process section calculates a representative color for each foreground pixel area, and extracts pixels having pixel values close to the representative color as foreground pixels.