1. An image processing device comprising: a memory that stores instructions; and one or more processors that execute the instructions to cause the image processing device to function as: an image acquisition unit configured to acquire an image; a depth information acquisition unit configured to acquire depth information relating to a depth distribution of the image acquired by the image acquisition unit; an image transformation unit configured to perform an image transformation process on the image acquired by the image acquisition unit through coordinate conversion; a depth information transformation unit configured to perform a transformation process on the depth information acquired by the depth information acquisition unit through coordinate conversion corresponding to the coordinate conversion performed on the image; a combination information generation unit configured to generate combination information based on the depth information transformed by the depth information transformation unit; and an image combination unit configured to combine a plurality of images transformed by the image transformation unit based on the combination information generated by the combination information generation unit.