Patent ID: 8358836

Claim:
A specific color detection circuit for judging whether an RGB input pixel is a signal in a predetermined color detection region having a color signal to be detected as a center thereof, comprising: a first distance calculation unit for showing an RGB input pixel and an RGB color signal to be detected in a three-dimensional coordinate with three axes of R axis, G axis and B axis, and calculating a distance, as a first distance, from an origin to a foot of a perpendicular drawn from the coordinate of the RGB input pixel to a straight line connecting the origin and the coordinate of the RGB color signal to be detected or a coordinate with the same RGB ratio as that of the RGB color signal to be detected; a second distance calculation unit for calculating a distance, as a second distance, from the coordinate of the RGB input pixel to the foot; a hue detection unit for detecting a hue of a signal of the RGB input pixel; a third distance calculation unit for generating a detection region in a color difference direction according to the first distance and the hue of the signal of the RGB input pixel, and calculating a third distance based on the first distance with respect to the detection region; and a judging unit for judging the RGB input pixel as being in the predetermined color detection region when the third distance is longer than the second distance as a result of a comparison between the second distance and the third distance.