Image processing device and control method for image processing device

When an original image containing a code image is lossy-compressed, the image quality of the code image is deteriorated. Thus, due to the deterioration of the image quality of the code image, information contained in the code image cannot be acquired. Thus, a portion corresponding to the code image is not lossy compressed, and the portion corresponding to the code image, which has not been subjected to lossy compression, is stored in a storage unit.