Patent ID: 7440138
Filing Date: 2008-10-21
Classification: H04N

Abstract:
1. A method for converting a digital color image to a digital gray value image so as to distinguish colors present in the color image, the digital color image being built up of pixels each having a color value and the digital gray value image being built up of pixels each having a gray value, the method comprising: converting the color values of the pixels to gray values by using a dynamically adapted conversion function which is generated on the basis of a comparison of color differences between a plurality of main color values of main colors in the digital color image and gray value differences corresponding to said color differences in the digital gray value image, said main color values being defined by a cluster analysis of the colors of the digital color image, wherein the adapted conversion function is a combination of a pre-defined naïve gray value conversion and a localized correction function, wherein the localized correction function has a value which decreases with a distance in a color space between a color for conversion and a corresponding main color; and printing, by a printing device, the converted gray values.