Chroma-preserved luma controlling technique using YCbCr color space

Abstract

YCbCr color space composed of luma and chominance components is preferred for its ease of image processing. However the non-orthogonality between YCbCr components induces unwanted perceived chroma change as controlling luma values. In this study, a new method was designed for the unwanted chroma change compensation generated by luma change. For six different YCC-hue angles, data points named 'Original data' generated with uniformly distributed luma and Cb, Cr values. Then the weight values were applied to luma values of 'Original data' set resulting in 'Test data' set followed by 'new YCC-chroma' calculation having miminum CIECAM02 ΔC between original and test data for 'Test data' set. Finally mathematical model is developed to predict amount of YCC-chroma values to compensate CIECAM02 chroma changes. This model implemented for luma controlling algorithm having constant perceived chroma. The performance was tested numerically using data points and images. After compensation the result is improved 51.69% than that before compensation when CIECAM02 Δ C between 'Original data' and 'Test data' after compensation is compared. When new model is applied to test images, there is 32.03% improvement.