BBHE is a well-known contrast-enhancement method for consumer electronics. However, in many cases, it tends to change significantly the brightness of the input image. Thus the quality of the output image will be degraded because of the annoying artifacts, such as over-enhancement, etc. In order to preserve the mean brightness of the input image and enhance the contrast efficiently, a novel method, BPWSI, is proposed in this paper. The basic idea of the proposed method is to combine two subimages in one brightness-preserving way. Experimental results on many images with low and high contrast show that BPWSI can preserve the mean brightness with higher accuracy than BBHE, DSIHE, RSIHE, RMSHE, CLAHE, and BHEPL-D. At the same time, contrast can be enhanced with less annoying artifacts than the above-mentioned methods. Analysis on Eqs. (21) and (26) indicates that the principle of BPWSI is quite simple, which makes it suitable for real-time systems.