METHOD, APPARATUS AND COMPUTER PROGRAM FOR ADAPTIVE BLACK POINT COMPENSATION

摘要

A system and method for carrying out improved spatial and color adaptive gamut mapping algorithms, based on image decomposition in two bands lhigh and Ilow using 5D bilateral filtering. A function g() applied to the low-pass band Ilowcarries out black point compensation followed by a gamut clipping algorithm. Function k() applied to Ihigh is a locally adaptive function for maintaining the relative content of the two bands in the output image. Hereafter the step of merging and adaptive mapping of IhighM and IlowM by 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.