METHOD FOR DETERMINING COLOR OF AN ILLUMINANT IN AN IMAGE BASED ON HISTOGRAM DATA

An electronic method measures the color cast of a digital representation of a natural scene. Colors of the natural scene are represented in digital electronic form as pixels. Neighborhoods of pixel colors in a chrominance histogram are isolated. Neighborhoods may be isolated by convolving the chrominance histogram with a two-dimensional filter. Lighting color from the scene is measured from isolated color neighborhoods by: a) determining lines in a chrominance plane which lie along major axis of isolated color neighborhoods, and b) selecting a convergence-chrominance value near which the detected lines converge. Lines in the chrominance plane may be weighted so that lines from neighborhoods that are more reliable indicators of lighting contribute more to the convergence-chrominance than less lines from less reliable neighborhoods. The image is then transformed so as to map the measured lighting value to another value, such as neutral.