Patent ID: 7417647

Claim:
A method for storing overlay pixels of an overlay image over background pixels of a background image, the overlay and background pixels being defined by at least a luminance component and at least one color component, wherein the at least one color component is shared between at least two pixels, the method comprising: defining a first luminance value corresponding to a transparent overlay pixel; defining a second luminance value corresponding to an opaque overlay pixel; storing the luminance component and discarding the at least one color component of an overlay pixel if the luminance component differs from the first and second luminance values, so as to over-write the luminance component and to leave remaining the color component of the corresponding background pixel; storing the luminance component and the at least one color component of an overlay pixel if the luminance component equals the second luminance value, so as to over-write both the luminance and the at least one color component of the corresponding background pixel; and discarding the luminance component and the at least one color component of an overlay pixel if the luminance component equals the first luminance value, so as to leave remaining the luminance and the at least one color component of the corresponding background pixel; wherein the luminance components of the overlay pixels range between a minimum and a maximum, the first luminance value being equal to one of the minimum and maximum, and the second luminance value being equal to the other one of the minimum and maximum.