1. An image processing apparatus comprising an image compression conversion unit to quantize an image having attribute data for each pixel, wherein when a region has the attribute data of a photographic image, the image compression conversion unit quantizes the region by a BTC method, wherein when a region has the attribute data of other than the photographic image, and the region is a halftone region, the image compression conversion unit quantizes the region by the BTC method, and wherein when a region has the attribute data of other than the photographic image, and the region is a high resolution region, the image compression conversion unit generates a density pattern for the region to quantize the region according to the generated density pattern.