According to an embodiment, provided is a controller that controls an image forming unit forming an image on a recording medium based on image data in which densities of a plurality of colors are specified for each pixel. The controller includes: a setting unit that sets a common representative value to a density of a specific color indicating one of the colors in each of a plurality of pixels included in a specific area indicating a specific area represented in the image data; and a determining unit that determines a density of each of the colors so that a sum of densities of the respective colors other than the specific color in the pixels included in the specific area becomes equal to or lower than a value acquired by subtracting the representative value from a reference value indicating a total amount restriction target of a total amount of toners.