Using a residual image to represent an extended color gamut digital image

DETAILED DESCRIPTION It is an object of the present invention to overcome the limitations of the prior art by permitting the storage of images in a color space having a limited color gamut, while retaining the extended color gamut information.
This object is achieved in a method for representing a digital image having color values with an extended color gamut in a storage color space having a limited color gamut comprising the steps of: a) adjusting the color values of the extended color gamut digital image to fit within the limited color gamut to form a limited color gamut digital image; b) representing the limited color gamut digital image in the storage color space; and c) determining a residual image representing a difference between the extended color gamut digital image and the limited color gamut digital image; and d) associating the residual image with the limited color gamut digital image in the storage color space such that the associated residual image and the limited color gamut digital image in the storage color space are adapted to be used to form a reconstructed extended color gamut digital image.
ADVANTAGES The present invention has the advantage that a digital image can be stored in a color space convenient for a particular application while overcoming the color gamut limitation associated with that color space.
The image can be stored, for example, in a video RGB color space that is well-adapted for fast and convenient display on a computer system without compromising the potential quality of the image.
It has the additional advantage that the use of the extended color gamut information is optional.
As a result, the benefits of the extended color gamut information can be gained by applications that are able to make use of it, without introducing an image quality or computation penalty for applications that do not require the optional information or that are not able to make use of it.