1. An image processing apparatus comprising: an image region dividing portion configured to divide a shot image into a plurality of image regions so that an amount of change of an image quality in each of the plurality of image regions is within a predetermined range when the shot image is blurred using a blur kernel depending on an object distance and an angle of view of the shot image; a blur kernel generating portion configured to generate a plurality of blur kernels for the respective image regions divided by the image region dividing portion; and an image processing calculating portion configured to generate a blur-added image by performing a convolution calculation for the shot image using the blur kernels generated by the blur kernel generating portion.