This paper proposes a calculation algorithm for a spatial gamut mapping technique for preserving the spatial ratios in an original image. McCann suggested the effectiveness for preserving ratios of colors at adjacent edges in the gamut mapping procedure. He also proposed a mapping algorithm based on the Retinex with two input images which are an original image with large gamut and a best image with limited gamut of the reproduction media. The proposed algorithm provides a concrete algorithm to obtain the reproduction image with preserving spatial ratios from only the input image by using the relaxation labeling technique. Experimental results show that the proposed method can work well for a Mondrian pattern.