1. An image processing apparatus for performing image processing more than once by using an extended region, comprising: an input unit configured to input image data and printer setting information of the image data; an extended region computing unit configured to divide the image data into a plurality of block regions and compute an extended region of one of the divided block regions for each image processing operation; a generating unit configured to generate a processed block region comprising one of the block regions and an extended region added thereto that is computed using the extended regions computed for each image processing operation performed on the one of the divided block regions; and a processing unit configured to perform image processing on the processed block region produced by the generating unit, wherein the extended region required in each image processing operation for the one of the divided blocks is determined based on a size of a filter derived from the printer setting information.