An image processing method includes storing image data in a storage unit; setting a common region in the storage unit, the common region including an input image data storage region and an output image data storage region; sequentially storing the image data that is compressed at a preset compression ratio in the input image data storage region; sequentially expanding the image data stored in the input image data storage region; temporarily storing the expanded image data in the output image data storage region; and controlling allocation of the input image data storage region and the output image data storage region in the common region. In an embodiment, the allocation of the input image data storage region and the output image data storage region in the common region may be determined depending on the compression ratio of the sequentially inputted image data.