Color-Line Regularization for Color Artifact Removal

Existing regularization functions for color image restoration cannot remove color artifact, undesirable appearance of colors, sufficiently, which degrades the quality of color images. In this paper, we propose a new regularization function, named the local color nuclear norm (LCNN), for removing color artifact in color image restoration. LCNN is designed to promote the local color-line property: the color distribution of each local region of a color image exhibits strong linearity. The local color-line property is inherent in clean color images and is violated by color artifact, so that suppressing LCNN is expected to reduce color artifact effectively. In addition, the very nature of LCNN allows us to incorporate it into various color image restoration formulations, where the associated optimization problems can be efficiently solved by proximal splitting techniques. Several illustrative applications of LCNN are presented with comprehensive experimental results.