An image processor includes an image degradation measuring unit configured to compute a degradation level of block data with respect to each of blocks within an image, a degradation determining unit configured to select, with respect to each of the blocks within the image, the block data of a target block of one of a plurality of the images based on degradation levels of respective block data of the target blocks of the plurality of the images, and an image synthesis unit configured to generate a sheet of an image by synthesizing the block data selected with respect to the blocks within the image.