The values of the primary color space components of an image signal, such as the components of RGB video signal, are maintained within their allowed range by modifying the signal in a different color space, such as YUV space. Specifically, the U and V chrominance components are attenuated by an attenuation factor g while the luminance component Y is not modified. The value of g is the largest possible value less than 1 that will cause all primary color space components that would otherwise be outside the allowed range to be within that range. A high quality of the displayed image is maintained.