1. An image processing apparatus comprising: an acquisition unit that acquires a statistical value of pixel values for each divided region obtained by dividing an input image; a determination unit that compares for each divided region the statistical value of the divided region acquired by the acquisition unit with a first threshold and determines whether the divided region is as color region or a monochrome region; and a re-determination unit that compares a statistical value of an adjacent divided region, which is a divided region, from among divided regions determined by the determination unit as monochrome regions, that is adjacent to the divided region determined by the determination unit as a color region, with a second threshold, by which a divided region is more likely determined as a color region than by the first threshold, for each adjacent divided region, and re-determines whether the adjacent divided region is a color region or a monochrome region.