Method, apparatus and computer program for adaptive black point compensation

Abstract

A system and method for carrying out improved spatial and color adaptive gamut mapping algorithms, based on image decomposition in two bands Iand Iusing 5D bilateral filtering. A function g( ) applied to the low-pass band Icarries out black point compensation followed by a gamut clipping algorithm. Function k( ) applied to Iis a locally adaptive function. The merging and adaptive mapping of Iand Iby function f( ) using local adaptive implementations of the two families of pointwise GMAs: compression and clipping is carried out. Two functions f( ) are proposed, they take into account the color properties of the neighborhood of each pixel. Black point compensation is adaptive by, in dependence of a histogram of the image, carrying out black point compensation if the number of pixels below the black point of the output device is more than a first threshold; carrying out partial black point compensation if the number of pixels below the black point of the output device is between the first and a second threshold and carrying out no black point compensation if the number of pixels below the black point is less than the second threshold.