RAW IMAGE PROCESSING SYSTEM AND METHOD

A method of image processing in a camera, said camera including an image capture system configured to convert received light into raw image data in the form of a mosaiced multiple colour image, the image capture system including an image sensor with a colour filter array, wherein the image sensor includes an array of pho-tosites, spatially correlated with filters of the colour filter array, so that each photosite has a corresponding spectrally selective filter, so as to receive light at a respective one of a plurality of colours in the colour filter array and output a pixel value indicating an intensity of light captured, wherein the method includes: passing the raw image data to an image processing subsystem configured to perform a range of image processing tasks, including encoding the raw image data into a desired video data format; by the image processing subsystem, prior to said encoding: generating a luminance image from the raw image data by computing a luminance value for each photosite by applying a first filter kernel to pixel values centered on said photosite, the first filter kernel representing weightings applied to a weighted sum of pixel values covered by the filter kernel, said luminance image having a first resolution and representing raw image data output from the image sensor; generating from the raw image data a first chrominance image representing raw image data output from the image sensor by applying a second filter kernel to pixel values centered on each photosite having pixel values of a first colour in the colour filter array, wherein pixel values in the first chrominance image comprise a difference be-tween pixel values of the first colour in the colour filter array and pixel values of a second colour in the colour filter array; and generating from the raw image data a second chrominance image representing raw image data output from the image sensor by applying the second filter kernel to pixel values centered on each photosite having pixel values of a third colour in the colour filter array, wherein pixel values in the second chrominance image comprise a difference between pixel values of the third colour in the colour filter array and pixel values of the second colour in the colour filter array.