Combined with the human visual characteristics,we propose an image e nhancement algorithm for the human eye.Objective function of the proposed algorithm is pixel pairs′ number,of which the gray-sc ale difference can be perceived by human eye.In order to keep the fidelity of image information,the enhancement process should be under the c ondition of maintaining the gray scale difference direction of the original image pixels.To maximize the objective function,the first step is to test the human eye maximum distinguishable gray levels towards specified monitor.The test should consider human eye brightness thresh old characteristics.Combined with the gray levels of the image itself and the maximum gray levels human eye can distinguish,we use a dyn amic programming algorithm to compress gray levels,so that the gray levels contained in the merged image would not be more than the ma ximum gray levels human eye can distinguish.Finally,the grays implement one to one mapping based on human visual brightness threshold ch aracteristics.Compared with the novel image enhancement algorithms,the proposed algorithm is fully considering the interacti on of human eye and the monitor brightness.Further more,the proposed algorithm has a clear objective function.Experimental results show tha t the proposed algorithm has better performance than the currently used image en hancement algorithms.