Image generation method, image generation apparatus, program, and storage medium

An image generation apparatus comprising:

• an image sensor configured to acquire an input image, wherein the image sensor has an array of a plurality of pixels, each of which has arranged therein a plurality of sub-pixels that each receive a light beam that passes through a different pupil sub-area of an imaging optical system;
• a first generation unit configured to generate a plurality of parallax images that respectively correspond to the different pupil sub-areas based on the input image;
• a second generation unit configured to generate a plurality of pixel shifted images by performing different shifting for each of the plurality of parallax images according to a virtual image forming plane of the imaging optical system that is different from an image sensing plane at which the image sensor is arranged;
• and
• a composition unit configured to generate an output image that has a higher resolution than the resolution of the parallax images from the plurality of pixel shifted images through composition processing.