1. An image processing device, comprising: an image acquisition part acquiring first image data; a character detector detecting, based on the first image data, data of a character area in the first image data; a marking detector detecting, based on the first image data, data of a marking area in the first image data; an image adjustment area determination part determining, based on a detection result of the character detector and a detection result of the marking detector, data of an image adjustment area in the first image data; and an image processing part subjecting the data of the image adjustment area in the first image data to image processing to output second image data.