An image processing apparatus quantizes multi-level image data of n colors, where n≧2, by performing an error diffusion processing. The image processing apparatus includes: a dot arrangement determining unit that determines either one of an essential dot count and an essential recording material amount when the multi-level image data of n colors is converted into multi-level image data of m colors, where n>m≧1, by the error diffusion processing; and a color arrangement determining unit that performs the error diffusion processing on each color component of the multi-level image data of n colors, calculates either one of a dot count and a recording material amount for each color component, and determines an arrangement of either one of the dot count and the recording material amount for each color component within a range of a corresponding one of the essential dot count and the essential recording material amount determined by the dot arrangement determining unit.