1. An image processing apparatus comprising: an acquiring unit configured to acquire a plurality of images to be combined; a first storage control unit configured to compress the plurality of images acquired by the acquiring unit with a first compression ratio and store the compressed plurality of images in a memory, the stored plurality of images including first combining images corresponding to combining portions of the respective plurality of images; a second storage control unit configured to store, in a memory, second combining images corresponding to the combining portions of the respective plurality of images in a non-compressed format or a compressed format compressed with a second compression ratio lower than the first compression ratio; a determining unit configured to determine a layout of the plurality of images stored by the first storage control unit, based on the second combining images corresponding to the combining portions stored by the second storage control unit; and an outputting unit configured to output the plurality of images, including the first combining images, which are compressed with the first compression ratio and stored in the memory by the first storage control unit, so that the plurality of images are combined according to the layout determined by the determining unit.