A disclosed image processing apparatus is capable of shifting an illegal copy preventing pattern so that an image reading device can recognize the pattern printed at the edge end of the printing range on a paper even when the printing range on the paper is changed by, for example, trimming and user settings. The apparatus includes an image output unit outputting an image to a prescribed region; an output position setting unit acquiring output region information, comparing the output region information with the illegal copy preventing pattern; and determining an output position of the illegal copy preventing pattern based on the comparison result, and a combining unit combining the illegal copy preventing pattern and image data based on the output position determined by the output position setting unit. The image output unit outputs the image combined by the combining unit.