Patent ID: 7652808

Claim:
A luminance dynamic range system comprising: an image processing module for transforming an input image into a luminance component L in and chrominance components, C 1 and C 2 ; a spatial low pass filter, responsive to L in for outputting a filtered luminance component L f , wherein L f is a function only of L in , wherein the low pass filter allows shadow regions to pass through as low luminance, and filters out detail in high-contrast regions; and a luminance compression module which performs gamut mapping that varies across different parts of the input image by spatially adapting a luminance compression function according to local image characteristics in such a manner as to preserve both shadow detail and overall image contrast, and is responsive to L f and L in for performing luminance compression on the luminance component L in to output a compressed luminance signal which is represented as an overall compression function L out that is within an achievable luminance range of an output device; wherein the luminance compression module combines two compression functions L comp1 (L in ) and L comp2 (L in ) via a blending function α(L f ), thereby, producing the overall compression function L out ; wherein the function L comp1 is optimized for preserving the overall image contrast and the function L comp2 is optimized for preserving the shadow detail; wherein the functions L comp1 (L in ) and L comp2 (L in ) are functions only of L in , and the functions α(L f ) is only a function of L f ; and wherein the functions L comp1 (L in ) are both designed such that the overall compression function L out is spatially smooth and maps a luminance dynamic range of the input image to a more limited luminance dynamic range of the output device.