Abstract: Aiming at differentiating computer graphics from natural image in a color image,color quantization is achieved by adaptive self-organizing maps and the number of colors is reduced to facilitate the subsequent segmentation and recognition of color images.Color planes are formed by extracting every kind of color and then transformed into b-i level image,where connected-components are labeled and their edges are detected.Afterwards the labeled connected-components and their edges are mapped back into the original color image to calculate inhomogeneity and edge contrast.Generally,inhomogeneity of artificial regions and edge contrast of natural regions are low.According to the ratio of inhomogeneity and edge contrast,all regions can be classified. Some experimental results verified the presented method.