Disclosed are an image processing apparatus and method in which it is possible to suppress density unevenness in the output of an image forming apparatus in a simple manner. A test image is printed out by a printer (13), the printout is read by an image reading processing unit (10), and an analyzing processing unit (17) detects the output characteristic (density unevenness, printing position deviation, etc.) of each of a plurality of print elements possessed by the printhead of the printer. A mask generating processing unit (11) generates a threshold-value mask which reflects the output characteristics detected by the analyzing processing unit and stores the mask in a mask memory (15). A halftoning processing unit (12) outputs image data to the printer after the image data is subjected to halftoning utilizing the threshold-value map that has been stored in the mask memory.