An image processing apparatus includes a count unit, a transform unit, a first calculation unit, a second calculation unit, and a binarization unit. The count unit counts the number of pixels of an original binary image. The transform unit transforms the original binary image into a transformed image based on a given transform level. The first calculation unit calculates the number of pixels of the transformed image, based on the given transform level and the number of pixels of the original binary image. The second calculation unit calculates a threshold level based on the number of pixels for each pixel value of the transformed image and the number of pixels of the transformed image. The binarization unit binarizes the transformed image based on the threshold level.