A pixel position to be mapped to each pixel position on an output image by deformation is obtained as an input pixel position. A filter coefficient group to be used for pixel interpolation at the time of deformation is adjusted by using the pixel values of pixels positioned around an input pixel position on the input image. A pixel value at the pixel position on the output image which corresponds to the input pixel position is calculated by using the pixel values of the pixels positioned around the input pixel position on the input image and the filter coefficient group after adjustment.