1. A method of detecting skin tone pixels in an input image and adjusting colour values thereof for an output image, the method comprising: determining for each of a plurality of pixels in an input image whether initial chromaticity values of each of said pixels lie within a skin tone area defined in a chromaticity plane; and, amending the initial chromaticity values of those pixels that have chromaticity values lying within said skin tone area to obtain amended chromaticity values for use in obtaining an output image.