Image denoising with hard color-shrinkage and grouplet transform

To remove signal-dependent noise of a digital color camera, we propose a new denoising method with our hard color-shrinkage in the tight-frame grouplet transform domain. The classic hard-shrinkage works well for monochrome-image denoising. To utilize inter-channel color dependence, a noisy image undergoes the color transformation from the RGB to the luminance-and-chrominance color space, and the luminance and the chrominance components are separately denoised; but this approach cannot cope with actual signal-dependent noise. To utilize the noise´s signal-dependencies, we have constructed the hard color-shrinkage where the interchannel color dependence is directly utilized in the RGB color space. The hard color-shrinkage alleviates denoising artifacts, and improves picture quality of denoised images.