Patent ID: 6104830
Filing Date: 2000-08-15
Classification: G06T,H04N

Abstract:
A method of analyzing and optionally correcting color casts or coloring errors in a digitally represented image, wherein each photograph is represented by a number of pixels or photographic points in a color space with separate chrominance and luminance dimensions, whereina) part of or all of the chrominance dimensions of the color space are examined to establish completely or partially hidden line of convergence structures,b) that two or more line-of-convergence structures are determined as parameterized functions, and thatc. on the basis of these line-of-convergence structures at least one mutual intersecting point is established for determining a color convergence of the digitally represented image; andwherein the examination of a Cartesian chrominance dimension of the color space comprises an approximation of a portion of or all of the image points to a parameterized function via a Hough-transformation; andwherein the image points in the color space are approximated to a straight line in a polar system of co-ordinates via a modified Hough-transformation according to the formulax cos .theta.+y sin .theta.=.rho.H.sub.log (a*,b*))wherein x and y designate the Cartesian representation in a plane of a color space, .theta. designates the angle to the axis of abscissa, .rho. is the angular distance from origin to the line, and wherein ##EQU4## the U(a*,b*) being a unit function which is summed up throughout the entire x,y-plane, wherein parameters a* and b* are the chrominance coordinates of the color space.