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 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 calculate the blur kernel for each image region 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 kernel calculated by the blur kernel generating portion.