Patent ID: 8508794

Claim:
An image processing method of forming an image, comprising: setting one of a plurality of modes including a monochrome mode and a color mode, wherein the monochrome mode is capable of forming a warm black tone image and capable of forming a cold black tone image and the color mode is capable of forming a color image; converting a multivalued luminance signal into signal values for forming the warm black tone image by using a warm black tone ink without using a cyan color ink, a magenta color ink and a yellow color ink in a case where the monochrome mode for the warm black tone image is set; converting the multivalued luminance signal into signal values for forming the cold black tone image by using a cold black tone ink without using the cyan color ink, the magenta color ink and the yellow color ink in a case where the monochrome mode for the cold black tone image is set; and converting the multivalued luminance signal into signal values for forming the color image by using the cyan color ink, the magenta color ink and the yellow color ink in a case where the color mode is set; wherein a color gamut of the warm black tone ink includes an upper right quadrant of an a-b plane in a Lab space, a color gamut of the cold black tone ink includes a lower left quadrant of the a-b plane in the Lab space, and the color gamut of the warm black tone ink and the color gamut of the cold black tone ink have hues that are opposite to each other.