1. An image processing apparatus comprising: a first generation portion that generates a first low-gradation image by performing a first process on an input image to reduce the number of gradations of the input image; a second generation portion that generates a second low-gradation image by performing a second process on the input image to reduce the number of gradations of the input image; a density detector that detects a density of the input image; a determination portion that determines, based on the density, a ratio at which the first low-gradation image and the second low-gradation image are blended together; and a mixing portion that blends the first low-gradation image and the second low-gradation image in accordance with the ratio.