1. An image processing apparatus comprising: an input unit configured to input a plurality of images; a setting unit configured to set a specific region on each of the plurality of images; a calculation unit configured to determine a typical size of the specific region of each of the plurality of images and to calculate a typical size ratio for each of the plurality of images, the typical size ratio indicating a ratio of the typical size to a size of the entire image of each of the plurality of images; a selection unit configured to select a typical size ratio to be used as a reference ratio from the typical size ratios calculated for the plurality of images; and a trimming unit configured to trim each of the plurality of images in accordance with a trimming region of the images with reference to the selected typical size ratio.