Mosaic image generation device, method, and program

There is provided a mosaic image generation technique that eliminates restriction on a material image corresponding to an object image and improves the visibilities of the mosaic image and the material image. A mosaic image generation device comprises: a dividing unit for dividing an object image, from which a mosaic image is generated, into a plurality of blocks; an object image processing unit for calculating, as a target density value, an average density value of each basic color in each of the blocks divided by the dividing unit; a decision unit for deciding from the plurality of blocks a layout block on which the material image is to be laid out, without being restricted by the image of the layout block; a calculation unit for calculating an average density value of each basic color in the material image; and a color correction unit for performing a color correction on the material image such that the average density value of each basic color in the material image becomes the target density value of each