r g b subpixels including a r subpixel a g subpixel and a b subpixel the maximum values of the r subpixel the g subpixel and the b subpixel of the pixels of each sample block can be extracted for instance a given sample block contains four pixels and the values of the r subpixel the g subpixel and the b subpixel of the four pixels are presented as 125 36 96 75 89 92 37 156 63 and 56 78 122 thus the maximum values of the r g b subpixels of that sample block are respectively 125 for the r subpixel 156 for the g subpixel and 122 for the b subpixel therefore the maximum values of the individual r g b subpixels of each sample block can be extracted through this way and denoted respectively as rmax 1 rmax 2 rmax 56 for the r subpixel gmax 1 gmax 2 gmax 56 for the g subpixel and bmax 1 bmax 2 bmax 56 f for the g subpixel after the values of the r g b subpixels have been extracted average values of each individual r g b subpixel of each sample block can be calculated as shown in step s 3 taking the aforementioned example the average value of all the r subpixel.