Abstract: An efficient method,named brightness-preserving weighted sub-images(BPWSI),is proposed in this paper for enhancing the contrast of color images.First,two sub-images are defined based on mean brightness preserving bi-histogram equalization(BBHE).Then,based on the mean brightness of the input image and two sub-images,weight coefficients of the sub-images are computed with brightness-preservation.Finally,the output image is generated as the weighted sum of the two sub-images.The experimental results on images with low and high contrast show that the proposed method can enhance color images efficiently and naturally without over enhancement or details lost which often happen in many other methods.