Monochrome image forming apparatus

A monochrome image forming apparatus that does not perform color printing and performs monochrome printing, comprising:

• an image data supply unit for a color image forming apparatus that has a function to write input color image data including plural primary color data components into color buffers;
• a color converter for the color image forming apparatus that comprises a color conversion unit configured to read the input color image data from the color buffers, perform an UCR process and a black generation process for the input color image data, and output output color image data including a black data component and plural primary color data components generated by the UCR process and the black generation process;
• and
• a controller configured to control the image data supply unit and the color conversion unit in accordance with a printing mode selected among a normal printing mode and an eco printing mode;
• wherein the color conversion unit performs the UCR process and the black generation process so as to make a toner consumption amount in the eco printing mode smaller than a toner consumption amount in the normal printing mode;
• the image data supply unit writes input monochrome image data of a single color to a monochrome buffer;
• and
• the color converter (a) reads out the input monochrome image data to the color conversion unit as the plural primary color data components of the input color image data in the eco printing mode, and (b1) performs the UCR process and the black generation process corresponding to the eco printing mode for the input monochrome image data using the color conversion unit in the eco printing mode.