A color chart is used to correct the color of an image. The color chart has a plurality of palettes, and each palette is differently colored. For each palette, the color of the region containing the palette in the image in which the color chart is carried is compared with the actual color of the palette to measure any change of the color that may have occurred in the process of image generation. Then, by correcting the color of the image so as to cancel out the change of the color, the color of the subject represented on the image can be corrected to appear natural.
For proper color correction, there is a need to identify the position of each palette on the image. In accomplishing this, in the prior art a user had to visually inspect the image displayed on a display, identify the region containing each palette of the color chart on the image, and enter information specifying the position and range containing each individual palette into an apparatus that carries out the color correction. However, the task of specifying the position and range for each individual palette has been troublesome for a user. To address this, various techniques have been proposed for detecting a color chart represented on an image (for example, refer to Japanese Laid-open Patent Publication No. 2002-152768, Japanese Laid-open Patent Publication No. H06-70345 and Japanese Laid-open Patent Publication No. 2010-226580).
For example, Japanese Laid-open Patent Publication No. 2002-152768 discloses a technique for detecting the position of a color chart by performing pattern matching on an image in which the color chart is represented.
On the other hand, Japanese Laid-open Patent Publication No. H06-70345 discloses a technique that converts each sampled image signal into a chromaticity signal and that determines whether the image is a color chart image or not by examining the distribution shape of the chromaticity signals.
Further, Japanese Laid-open Patent Publication No. 2010-226580 discloses a technique that identifies a color reference pattern from an image captured of a two-dimensional code containing the color reference pattern and that extracts the color information to be used for color correction.