1. A method of transforming input image data from an image sensor, said input image data having a plurality of pixels corresponding to a plurality of color channels, said method comprising: calculating a color channel gain for a first color channel of said plurality of color channels using a processing circuit by dividing a sum of gray world summary chromaticity values corresponding to the other color channels of said plurality of color channels by a sum of chromaticity values representing a neutral white point; and applying the color channel gain to said first color channel of said input image data.