Gamut mapping using luminance parameters

A colour processor for mapping an image from source to destination colour gamuts has an input for receiving a source image including a plurality of source colour points expressed according to the source gamut; a colour characterizer configured to, for each source colour point in the source image, determine a position of intersection of a curve with the boundary of the destination gamut; and a gamut mapper configured to, for each source colour point in the source image: if the source colour point lies inside the destination gamut, apply a first translation factor to translate the source colour point to a destination colour point within a first range of values; or if the source colour point lies outside the destination gamut, apply a second translation factor, different to the first translation factor, to translate the source colour point to a destination colour point within a second range of values.