1. An image processor comprising: an edge detection filter for detecting an edge amount in a first predetermined area which corresponds to a density difference between a specified pixel and other pixels surrounding the specified pixel, said edge amount being used for correcting image data of the specified pixel; judging means for judging whether all of the specified and surrounding pixels have a same level in a second predetermined area smaller than said first predetermined area, said second predetermined area including said specified pixel; and invalidation means for making said detected edge amount invalid when all of the pixels in the second predetermined area have the same level, regardless of the level of all of the pixels of the first predetermined area, prior to the correction of image data.