In case of an image region having a property of abrupt changes in luminance and tint, even when a region made up of pixels having luminance values and tint levels similar to those of one point designated by the user is extracted as a correction region with reference to the user designated point, it is difficult to extract a region to be corrected without omission. To solve this problem, a user instruction indicating a point inside or near an image region which is to undergo correction is input, and a plurality of origin pixels corresponding to start points of region expansion are set in a region which includes the input point and has a predetermined size. The region expansion is executed from each origin pixel, and a correction region is decided according to the result of the region expansion.