IMAGE PROCESSING APPARATUS AND COMPRESSION METHOD THEREFOR

An input image is divided into a plurality of predetermined sized image pieces, and code data indicating an arrangement pattern of color data included in each image piece and color data for the number of colors included in each image piece are output as first output data. When the first output data has a size greater than or equal to a predetermined data size, according to the number of image pieces by counted number of colors and priority of a pattern for color reduction, a pattern for color reduction relating the plurality of image pieces is determined. Among the divided image pieces, color-reduction processing is performed on an image piece corresponding to the determined pattern. Then, code data indicating an arrangement pattern of color data included in each image piece and code data for the number of colors included in each image piece are output as second output data.