Image processing apparatus and image forming apparatus which recognize orientation of document image

摘要

An image processing apparatus is provided with a binarization processing unit separately from a pseudo gradation processing unit that binarizes image data of a document image according to an error diffusion method. The binarization processing unit binarizes the image data of the document image using a threshold that is set higher than a threshold used by the pseudo gradation processing unit, with each threshold representing a different predetermined density level. Histograms showing the density distribution of the document image are generated from the image data binarized by the binarization processing unit. The orientation of the document image is recognized by the histograms.