Gamut mapping is applied to a pixel to thereby convert input component values (e.g. RGB values) of the pixel to corresponding output component values of the pixel. The input component values have a first valid range which includes some negative values and the output component values have a second valid range which does not include negative values. The gamut mapping unit determines whether a first input component value of the pixel is negative, and if so: (i) applies an adjustment to that component value such that it is not negative; and (ii) adjusts one or more other input component value(s) of the pixel based on the adjustment applied to the first input component value to thereby compensate for the adjustment applied to the first input component value. The output component values of the pixel are based on the adjusted input component values of the pixel.