An image forming apparatus adapted to combine a stamp image with an original image, said image forming apparatus comprising: - a stamp shape data generation unit configured to generate stamp shape data indicating a shape of the stamp image; - a stamp combining unit configured to combine the stamp shape data with image data formed of planes (21a, 21b, 21c) of a respective plurality of color components; - an output execution unit configured to execute an output based on the image data with which the stamp shape data has been combined by means of the stamp combining unit; and - an operation unit configured to input an instruction for the output, characterized in that the stamp shape data generation unit is configured to generate 1-bpp raster data based on a font serving as a base of the stamp image, wherein the stamp shape data generation unit is further configured to convert the 1-bpp raster data into raster data having a bit depth corresponding to a plane of the image data (21a, 21b, 21c), to thereby generate the stamp shape data on one monochrome plane, wherein the stamp shape combining unit is further configured to adjust, in order, the stamp shape data such as to have a density of the same color component (22a, 22b, 22c) of the stamp image for each of the plurality of color components of the planes of the image data (21a, 21b, 21c), and combine the adjusted stamp shape data with the corresponding color component of the planes of the image data (21a, 21b, 21c), and wherein the density of each of the plurality of color components of the stamp image are designated in the instruction for the output involving the combining through the operation unit along with the stamp image to be combined. - a stamp shape data generation unit configured to generate stamp shape data indicating a shape of the stamp image; - a stamp combining unit configured to combine the stamp shape data with image data formed of planes (21a, 21b, 21c) of a respective plurality of color components; - an output execution unit configured to execute an output based on the image data with which the stamp shape data has been combined by means of the stamp combining unit; and - an operation unit configured to input an instruction for the output, characterized in that the stamp shape data generation unit is configured to generate 1-bpp raster data based on a font serving as a base of the stamp image, wherein the stamp shape data generation unit is further configured to convert the 1-bpp raster data into raster data having a bit depth corresponding to a plane of the image data (21a, 21b, 21c), to thereby generate the stamp shape data on one monochrome plane, wherein the stamp shape combining unit is further configured to adjust, in order, the stamp shape data such as to have a density of the same color component (22a, 22b, 22c) of the stamp image for each of the plurality of color components of the planes of the image data (21a, 21b, 21c), and combine the adjusted stamp shape data with the corresponding color component of the planes of the image data (21a, 21b, 21c), and wherein the density of each of the plurality of color components of the stamp image are designated in the instruction for the output involving the combining through the operation unit along with the stamp image to be combined.