1. An image processing apparatus that outputs a transformed image obtained by performing geometric transformation on an input image, the image processing apparatus comprising: an identification unit configured to identify, on the basis of inverse parameters of the geometric transformation, a plurality of second sets of coordinates in the input image corresponding to a plurality of first sets of coordinates in the transformed image located within a certain distance from a first set of coordinates; a control unit configured to specify, among a plurality of third sets of coordinates located within the certain distance from a second set of coordinates in the transformed image, one or more sets of coordinates that overlap the plurality of first sets of coordinates in the transformed image located within the certain distance from the first set of coordinates, and to determine, among the plurality of second sets of coordinates identified by the identification unit, one or more sets of coordinates in the input image corresponding to the specified one or more sets of coordinates, and to cause a memory to store the specified one or more sets of coordinates and the determined one or more sets of coordinates associated with each other; and a generation unit configured to generate the transformed image by determining pixel values corresponding to the first set of coordinates in the transformed image based on pixel values corresponding to the plurality of second sets of coordinates identified by the identification unit, and pixel values corresponding to the second set of coordinates in the transformed image based on pixel values corresponding to the sets of coordinates including the determined one or more sets of coordinates in the input image stored in the memory.