Patent ID: 8355566

Claim:
A method for use in converting a colour image data indicative of a plurality of colour image regions defining a two-dimensional colour image, into a grayscale image data indicative of a plurality of grayscale image regions defining a two-dimensional grayscale image, each of the colour image regions corresponding to one of the grayscale image regions, and wherein a luminance information and a two-dimensional chromatic information is associated with each of the colour image regions, the method including the steps of: (i) determining a principal chromatic component of each of the colour image regions by reference to the two-dimensional chromatic information associated with each of the colour image regions; (ii) determining a first correlation value indicative of a correlation between the principal chromatic components of the colour image regions and the luminance informations of the colour image regions; and (iii) generating the grayscale image data by reference to the first correlation value, wherein: (a) if the first correlation value is equal to or greater than zero, a grayscale value is generated for each grayscale image region by adding the principal chromatic component to the luminance information associated with the corresponding colour image region; and (b) if the first correlation value is less than zero, a grayscale value is generated for each grayscale image region by subtracting the principal chromatic component from the luminance information associated with the corresponding colour image region.