An apparatus for image processing including a region detector, a density conversion unit, a compression unit, and an expansion unit. The region detector detects an edge region in an image data. The density conversion unit reduces a density difference within the edge region detected by the region detector. The compression unit compresses the image data within the edge region where the density difference is reduced by the density conversion unit, using the discrete cosine transform. The expansion unit expands the image data compressed by the compression unit.