Abstract: Shading measurement of dyeing products is the key to quality assessment. Different illuminants will lead to different color evaluation errors. In this paper we introduce a new illumination correction algorithm based on spherical harmonic theory into the color difference detection of dyeing products. Firstly, the collected images under the same light source are computed using the color constancy algorithm; then the R/S values of the dyeing products are measured under different illuminants and the spectral energy estimation and illumination compensation are done based on spherical harmonic theory; Finally, two shading evaluation formulas CMC(2:1) and CIE1976L*a*b* commonly used in textile industry are adopted to analyze the image processing effects of the above two algorithms. Experimental results show that whiling being used in color difference, the proposed method can reduce the evaluation errors caused by inconsistent illuminations and improve the integrity of quality evaluation of the dyeing products through achieving the mutual conversion of images between light sources.

Key words: color difference , spherical harmonic , illumination correction