1. An image processing apparatus comprising: a division unit configured to divide an input image into a plurality of tiles of a predetermined size; a resolution conversion unit configured to convert the input image into a low-resolution image; a determination unit configured to determine an attribute of a tile of interest from a pixel feature in the tile of interest, the tile of interest being included in the plurality of tiles obtained by the division unit dividing the input image; a generation unit configured to generate a histogram for pixels in a low-resolution tile that is obtained by converting an image of the same region as the tile of interest into a low-resolution image, the histogram indicating a relationship between each color of pixels and the number of pixels of that color; and a color-reduction processing unit configured to perform color reduction processing on the input image based on the histogram generated by the generation unit and the attribute determined by the determination unit.