Color Recovery from Multi-Spectral NIR Images Using Gray Information

Converting near-infrared (NIR) images into color images is a challenging task due to the different characteristics of visible and NIR images. Most methods of generating color images directly from a single NIR image are limited by the scene and object categories. In this paper, we propose a novel approach to recovering object colors from multi-spectral NIR images using gray information. The multi-spectral NIR images are obtained by a 2-CCD NIR/RGB camera with narrow NIR bandpass filters of different wavelengths. The proposed approach is based on multi-spectral NIR images to estimate a conversion matrix for NIR to RGB conversion. In addition to the multi-spectral NIR images, a corresponding gray image is used as a complementary channel to estimate the conversion matrix for NIR to RGB color conversion. The conversion matrix is obtained from the ColorChecker's 24 color blocks using polynomial regression and applied to real-world scene NIR images for color recovery. The proposed approach has been evaluated by a large number of real-world scene images, and the results show that the proposed approach is simple yet effective for recovering color of objects.