Gamut mapping using luminance parameters

A method of mapping a source colour point expressed according to a source colour gamut to a destination colour point expressed according to a destination colour gamut, the method comprising:

• determining a first scaling parameter in dependence on a curve that passes through the source colour point, the boundary of the source colour gamut and the boundary of the destination colour gamut;
• determining a second scaling parameter in dependence on the curve;
• calculating a first translation factor in dependence on the first and second scaling parameters;
• calculating a second translation factor in dependence on the first scaling parameter;
• determining whether the source colour point lies inside or outside the destination colour gamut, and
• in response to determining that the source colour point lies inside the destination colour gamut, applying the first translation factor so as to translate the source colour point to a destination colour point within a first range of values on the curve, or
• in response to determining that the source colour point lies outside the destination colour gamut, applying the second translation factor so as to translate the source colour point to a destination colour point within a second range of values on the curve;
• wherein the first and second ranges of values lie within the destination colour gamut.

A non-transitory machine readable storage medium having stored thereon machine readable instructions that, when processed at a computer system, cause the computer system to implement a method of mapping a source colour point expressed according to a source colour gamut to a destination colour point expressed according to a destination colour gamut, the method comprising:

• determining a first scaling parameter in dependence on a curve that passes through the source colour point, the boundary of the source colour gamut and the boundary of the destination colour gamut;
• determining a second scaling parameter in dependence on the curve;
• calculating a first translation factor in dependence on the first and second scaling parameters;
• calculating a second translation factor in dependence on the first scaling parameter;
• determining whether the source colour point lies inside or outside the destination colour gamut, and
• in response to determining that the source colour point lies inside the destination colour gamut, applying the first translation factor so as to translate the source colour point to a destination colour point within a first range of values on the curve, or
• in response to determining that the source colour point lies outside the destination colour gamut, applying the second translation factor so as to translate the source colour point to a destination colour point within a second range of values on the curve;
• wherein the first and second ranges of values lie within the destination colour gamut.