Patent ID: 8059712

Claim:
A method for compressing a digital image, comprising: performing by a computer: obtaining the digital image in a de-correlated color space comprising separate channels, including a luminance channel and chrominance channels; compressing the digital image into a bit stream, wherein the bit stream comprises: a compression of the luminance channel into a luminance bit stream; and a compression of the chrominance channels into a chrominance bit stream; mapping a received quality number for the luminance channel to a target bit rate for the luminance channel that is a fraction of the length of the luminance bit stream; mapping a received quality number for the chrominance channels to a target bit rate for the chrominance channels that is a fraction of the length of the chrominance bit stream; and supplying both the target bit rate for the luminance channel and the target bit rate for the chrominance channels to a rate distortion optimizer which performs a rate-distortion optimization separately on the luminance and chrominance channels of the bit stream to determine which portions of the luminance bit stream to include in compressing the luminance bit stream into a rate-distortion optimized luminance bit stream whose length does not exceed the target bit rate for the luminance channel and which portions of the chrominance bit stream to include in compressing the chrominance bit stream into a rate-distortion optimized chrominance bit stream whose length does not exceed the target bit rate for the chrominance channels.