1. An image processing apparatus comprising: a CPU that is configured to acquire a position and a size of a target photographic subject in an original image acquired by image capturing generate mask information indicating a relation between (i) a position to be subjected to predetermined image processing in the original image and (ii) strength of the predetermined image processing, based on the acquired position and the acquired size of the target photographic subject; and generate a new image by performing predetermined image processing of a different strength on each position in the original image by using the generated mask information.