1. A method of de-mosaicing an image mosaic to form a full colour image, the image mosaic being composed of a plurality of image pixels and each image pixel having one of at least three colour values and having a luminance value representing the intensity of the colour value for that pixel in the image mosaic, the pixels of each colour value being interleaved across the image mosaic with pixels of different colour values to form the image mosaic, the method comprising the steps of: i) for each colour value, generating from the pixels for that colour value a low spatial frequency monochrome image; ii) for each colour value, generating from the pixels for that colour value a high spatial frequency luminance image that extends only across pixels locations of the image mosaic for that colour value; iii) combining each of the high spatial frequency luminance images with a corresponding low spatial frequency monochrome images to form the full colour image.