Image forming apparatus utilizing a concenteration ratio of colors

An image forming apparatus capable of forming a color image on an image carrier with use of developers of a plurality of different developing colors, comprising:

• a plurality of developing devices respectively housing the developers of different colors;
• and
• a control section for controlling operation of the developing devices based on inputted image data,
• wherein the control section includes a concentration ratio recognition section for recognizing a concentration ratio of the respective colors for image data of every sheet from the image data, and controls so as to spare at least one color developer among the developers in response to the concentration ratio of respective colors recognized by the concentration ratio recognition section,
• wherein when the respective developing colors include cyan, magenta, yellow and black, and the concentration ratio is 0 to 17% in cyan, 65 to 100% in magenta, 36 to 100% in yellow, and 0 to 4% in black, a portion of the image data corresponding to these conditions is subjected to image formation only with a magenta developer.

An image forming apparatus capable of forming a color image on an image carrier with use of developers of a plurality of different developing colors, comprising:

• a plurality of developing devices respectively housing the developers of different colors;
• and
• a control section for controlling operation of the developing devices based on inputted image data,
• wherein the control section includes a concentration ratio recognition section for recognizing a concentration ratio of the respective colors for image data of every sheet from the image data, and controls so as to spare at least one color developer among the developers in response to the concentration ratio of respective colors recognized by the concentration ratio recognition section,
• wherein when the respective developing colors include cyan, magenta, yellow and black, and the concentration ratio is 57 to 91% in cyan and 34 to 81% in magenta, a portion of the image data corresponding to these conditions is subjected to image formation only with a cyan developer.

An image forming apparatus capable of forming a color image on an image carrier with use of developers of a plurality of different developing colors and transferring the formed color image so as to form the color image on a sheet, comprising:

• a plurality of developing devices respectively housing the developers of different colors;
• a calculation section for calculating, based on inputted image data, a concentration ratio of the respective colors for every dot to be formed on an image;
• and
• a control section for controlling operation of the developing devices so that when a ratio of a certain color calculated by the calculation section for all the dots to be formed for one sheet is lower than a predetermined value, the developing device of the color is not used,
• wherein the control section identifies a highest concentration from the concentration ratio of respective colors calculated by the calculation section, and controls operation of the developing devices so that the developers of at least one other color whose relative concentration ratio to the identified highest concentration is below a predetermined value.