An apparatus for processing an image includes a memory and a processor coupled to the memory. The processor is configured to determine a base hue value based on a state of distribution of a first hue value of each pixel of at least one image. The processor is configured to convert the first hue value of each pixel of the at least one image into a second hue value based on the base hue value. The processor is configured to calculate a difference in the second hue value between pixels included in each of a plurality of pixel pairs set in at least one feature region in the at least one image. The processor is configured to calculate a local feature amount of each of the at least one feature region based on the difference in the second hue value.