Restoration of a high ISO-sensitivity color image with the shift-invariant Haar wavelet transform

摘要

Recently, R. H. Chan, T. F. Chan, L. Shen, and Z. Shen proposed an image-restoration method, referred to as the C~2-S~2 method, in the shift-invariant Haar wavelet transform domain. The C~2-S~2 method is suitable for image-restoration in a digital color camera and restores a sharp color image in a lightly noisy case; but in a heavily noisy case it produces colored artifacts originating from noise. In such a case, the image-restoration process should be split into a color-interpolation stage, a denoising stage, and a deblurring stage; and along this line we present an approach to restore a high ISO-sensitivity color image. Our approach firstly de-mosaics observed color data with the bi-linear interpolation method, which is robust against observation noise but causes image blurs. Next, our approach applies our previously-proposed spatially-adaptive soft color-shrinkage to each shift-invariant Haar wavelet coefficient of the demosaicked color-image, to produce a denoised color-image. Finally, our approach applies to the denoised color-image a color-image restoration method that corresponds to an extension of the C~2-S~2 method and employs our previously proposed soft color-shrinkage. The experimental simulations conducted on raw color data observed with a SLR digital color camera with 6400 ISO-sensitivity demonstrate that our approach restores a high-quality color image even in a high ISO-sensitivity case, without producing noticeable artifacts.