The image processing method converts an input image to a transformed image. The method includes segmenting the transformed image into multiple blocks each having multiple pixels including multiple vertex pixels; providing a memory storing at least one coordinate in the transformed image for each vertex pixel, wherein plural coordinates are stored for at least one of the vertex pixels of at least one of the blocks; determining a coordinate in the input image corresponding to a vertex pixel of a focused block by reference to the memory, wherein when plural coordinates are stored for the vertex pixel, one of the coordinates is selected; repeating the determining step for all the blocks to determine coordinates in the input image corresponding to the vertex pixels; and determining coordinates in the input image for all the pixels of the multiple blocks by performing an interpolation processing using the coordinate values determined.