level is calculated accordingly the range of the gray scale level can be changed from 0 u02dc 255 to 0 u02dc 63 and the hardware resources can be saved referring to fig4 which is a flowchart of the image processing method of the first preferred embodiment of the invention in view of fig2 and fig3 the image processing method of the invention is applied to adjust the gray scale level of the jth pixel of the ith image frame of the video sequence inputted in the display system according to the first preferred embodiment of the invention as described above the image processing method includes the following steps step s 100 using a mask to smooth each pixel of each image frame step s 102 calculating a current maximum gray scale level and a current minimum gray scale level in accordance with the gray scale levels of the ith image frame step s 104 calculating an average maximum gray scale level in accordance with all the maximum gray scale levels of the image frames previous to the ith image frame and the current maximum gray scale level and calculating an average minimum gray scale level in accordance with all the minimum gray scale levels of the image frames previous to the ith image frame and the current minimum gray scale level step s 106 calculating a first gain according to the average maximum gray scale level and calculating a second gain according to the average minimum gray scale level step s 108 judging whether the jth pixel of the ith image frame is black if yes proceeding to step s 110 otherwise proceeding to step s 112 step s 110 adjusting the gray scale level of each color component.