1. An image processing method for converting an input image to a transformed output image consisting of multiple pixels, comprising: segmenting the transformed output image into multiple blocks each having multiple pixels including multiple vertex pixels; determining a coordinate value in the input image corresponding to one of the multiple vertex pixels of a focused block of the multiple blocks by reference to a vertex data memory, which stores at least one coordinate value in the output image for each of the multiple vertex pixels of each of the multiple blocks and in which two or more coordinate values are stored for at least one of the multiple vertex pixels of at least one of the multiple blocks, wherein when two or more coordinate values are stored for the one of the vertex pixels, one of the multiple coordinate values is selected; repeating the coordinate value determining step for all of the multiple blocks to determine coordinate values in the input image corresponding to the multiple vertex pixels of the multiple blocks of the transformed output image; and determining coordinate values in the input image for all of the multiple pixels of the multiple blocks by performing an interpolation processing using the coordinate values for all of the multiple vertex pixels of the multiple blocks.