Patent ID: 7280691

Claim:
Digital image processing apparatus for applying pixel-based colour correction to a hue-saturation-based polar representation of pixels of an input image to generate an output image, said apparatus comprising: colour correction logic arranged to provide a colour mapping operation defined by a hue alteration amount and a key value associated with each pixel; said colour correction logic comprising: hue modifying logic for adding a proportion of said hue alteration amount to a hue of each pixel of said input image, said proportion depending on said key value associated with that pixel; and saturation modifying logic for modifying a saturation of each pixel in dependence on said hue alteration amount and said key value for that pixel, such that for a key value indicating that only a fraction of said hue alteration amount should be applied to a current pixel, said saturation of that pixel is also modified so that, when expressed with respect to a rectangular chrominance-based colour space, said pixel is moved to a position in that colour space substantially lying on a straight line between an original position of said pixel and a position that said pixel would occupy if said full hue alteration amount were applied.