1. An image processing device, comprising: a processor controlling one or more components of the image processing device; a region extraction unit for separating and extracting a character region, a graphic region and a photograph region from image data; a region compression unit for performing a compression process for each of the region data extracted by said region extraction unit; a region synthesis unit for synthesizing the region data compressed by said region compression unit; and an image size calculation unit for calculating an image size of specific region data extracted by said region extraction unit; said region compression unit using, when the image size of the specific region data calculated by said image size calculation unit is equal to or greater than a threshold value, a first compression method to perform the compression process for the specific region data, and said region compression unit using, when the image size of the specific region data calculated by said image size calculation unit is smaller than the threshold value, a second compression method to perform the compression process for the specific region data; wherein the first compression method is a compression method in which the image size after the compression process is greater than the image size before the compression process, if it is applied to the specific region data whose image size before the compression process is smaller than the threshold value, and wherein the second compression method is a compression method in which the image size after the compression process is not greater than the image size before the compression process, if it is applied to the specific region data whose image size before the compression process is smaller than the threshold value.