1. A signal processing unit configured to convert image data from a lower bit depth representation to a higher bit depth representation, the signal processing unit comprising: a processor configured to: identify pixels in a saturation region wherein a color model value of each individual pixel in the saturation region is one of: above an upper saturation threshold and below a lower saturation threshold; and adjust the color model value of one or more of the individual pixels in the saturation region by a corresponding adjustment, a magnitude of each adjustment dependent, at least in part, on a number of pixels between the corresponding individual pixel and an edge of the saturation region.