Patent ID: 6654055
Filing Date: 2003-11-25
Classification: H04N

Abstract:
A method for detecting illumination color from a color image signal comprising the steps of:inputting a color image signal from an image input apparatus; removing saturated signals, signals with low brightness, and signals with high chroma from said color image signal; performing multistage median filtering to remove noise using edge maintenance information from said color image signal; transforming color signals R, G, B of all pixels of said color image signal into chromaticity coordinates; calculating a magnitude of a gradient to get color edges from the chromaticity coordinates of said color image signal; determining color transition bands as approximated lines; calculating eigen values and corresponding eigen vectors of each color transition band; determining if a ratio of a bigger eigen value to a total variance value is greater than a first predetermined limit condition; determining if an absolute magnitude of the bigger eigen value is greater than a second predetermined limit condition; finding a linear approximation equation of each color transition band using the eigen vector corresponding to said bigger eigen value; determining if all color transition bands are processed; calculating all intersection points between each pair of approximated lines; and determining the illumination color as average chromaticity coordinates of intersection points of each pair of two lines for which the product of the slopes is negative.