US Patent 7551318 Image processing apparatus and image processing method

The gray axis is adjusted such that an optimal representation can be achieved for low saturation colors close to the gray axis. A test pattern including a plurality of images, which have different color tones is printed, and a user selects a most desirable image. The gray axis of an image recording system is adjusted depending on which image is selected. Each of the plurality of images of the test pattern is a photographic color image represented mainly by low saturation colors close to achromatic colors along the gray axis. In accordance with the selected image, the gradation adjustment is performed for each ink color of the image recording system thereby adjusting the gray axis and the tone of colors close to the gray axis.