An image forming apparatus (1500, 1501) configured to form an image on a recording medium using a black color material and a plurality of chromatic color materials, the image forming apparatus comprising: generation means (1605, 1606) configured to generate black color material data for arranging dots of the black color material on the recording medium and a plurality of pieces of chromatic color material data for arranging dots of each of the plurality of chromatic color materials on the recording medium, based on input image data; and formation means configured to form an image on the recording medium using the black color material and the plurality of chromatic color materials based on the black color material data and the plurality of pieces of chromatic color material data, characterized in that the generation means (1605, 1606) further comprising: color separation means configured to convert the input image data into color material signal values for each of the black color material and the plurality of chromatic color materials by using a color separation table; and halftone means configured to convert the color material signal values determined by the color separation means into binary data based on which the image forming apparatus can perform recording; wherein a black color material line in the color separation table is set in such a way as to equalize a sum of the color material signal value of the black color material and a largest signal value of the color material signals of chromatic color materials to the maximum value of input image data; wherein the generation means (1605, 1606) is configured to generate the plurality of pieces of chromatic color material data, for each color positioned at a surface of a dark portion in a color gamut that can be reproduced using the black color material and the plurality of chromatic color materials, in such a way as to set the number of specific colors of the plurality of chromatic color materials whose dots are not overlapped with each other and arranged exclusively with dots of other chromatic color materials on the recording medium to be equal to or less than one color, and paper white is substantially covered with any one of the color materials. generation means (1605, 1606) configured to generate black color material data for arranging dots of the black color material on the recording medium and a plurality of pieces of chromatic color material data for arranging dots of each of the plurality of chromatic color materials on the recording medium, based on input image data; and formation means configured to form an image on the recording medium using the black color material and the plurality of chromatic color materials based on the black color material data and the plurality of pieces of chromatic color material data, characterized in that the generation means (1605, 1606) further comprising: color separation means configured to convert the input image data into color material signal values for each of the black color material and the plurality of chromatic color materials by using a color separation table; and halftone means configured to convert the color material signal values determined by the color separation means into binary data based on which the image forming apparatus can perform recording; wherein a black color material line in the color separation table is set in such a way as to equalize a sum of the color material signal value of the black color material and a largest signal value of the color material signals of chromatic color materials to the maximum value of input image data; wherein the generation means (1605, 1606) is configured to generate the plurality of pieces of chromatic color material data, for each color positioned at a surface of a dark portion in a color gamut that can be reproduced using the black color material and the plurality of chromatic color materials, in such a way as to set the number of specific colors of the plurality of chromatic color materials whose dots are not overlapped with each other and arranged exclusively with dots of other chromatic color materials on the recording medium to be equal to or less than one color, and paper white is substantially covered with any one of the color materials. color separation means configured to convert the input image data into color material signal values for each of the black color material and the plurality of chromatic color materials by using a color separation table; and halftone means configured to convert the color material signal values determined by the color separation means into binary data based on which the image forming apparatus can perform recording; wherein a black color material line in the color separation table is set in such a way as to equalize a sum of the color material signal value of the black color material and a largest signal value of the color material signals of chromatic color materials to the maximum value of input image data; wherein the generation means (1605, 1606) is configured to generate the plurality of pieces of chromatic color material data, for each color positioned at a surface of a dark portion in a color gamut that can be reproduced using the black color material and the plurality of chromatic color materials, in such a way as to set the number of specific colors of the plurality of chromatic color materials whose dots are not overlapped with each other and arranged exclusively with dots of other chromatic color materials on the recording medium to be equal to or less than one color, and paper white is substantially covered with any one of the color materials.