PROBLEM TO BE SOLVED: To provide an image processor improving the processing speed of image registration.SOLUTION: An image processing system aligning a floating image with a reference image includes: a first means for generating a one-dimensional histogram of pixel values of the reference image and storing, in a storage device, the positions of pixels belonging to each bin of the generated histogram of the reference image a second means for carrying out processing for converting the coordinates of the floating image according to predetermined geometric conversion information and generating, on a local memory, a one-dimensional histogram of the floating image indicating the frequency of pixel values of pixels of the converted floating image corresponding to the positions of the pixels of the reference image belonging to one bin of the generated histogram of the reference image and a third means for generating a two-dimensional connection histogram of the floating image by combining the generated one-dimensional histogram of the floating image.
