1. An image processing apparatus comprising: an extracting unit for extracting an edge area of an image; an edge correction unit for, based on a level of a pixel value of the edge area of the image, correcting the pixel value of the edge area of the image; and a halftone processing unit for carrying out a first halftone processing on the edge area of which the pixel value has been corrected and a second halftone processing on an area of the image that is different from the edge area, the second halftone processing being different from the first halftone processing; wherein the second halftone processing is a first screen processing, and the first halftone processing is one of a contone process and a second screen processing that uses a screen of which a number of screen lines is different from a number of screen lines of a screen used by the first screen processing.