1. The image processing method comprising: storing a plurality of first pixels of a previous image and a plurality of second pixels of a current image in a sampling window; calculating a plurality of pixel differences between the plurality of first pixels of the previous image and the plurality of second pixels of the current image in the sampling window, and generating a total pixel difference according to a sum of the plurality of pixel differences; wherein the second pixel is at a position corresponding to the first pixel; deciding a first blending value of a pixel of in the sampling window and determining whether the pixel is a static pixel or a moving pixel according to the total pixel difference; determining a second blending value when the pixel is a static pixel; and calculating the current image and the previous image using weighted average according to the first blending value so as to generate and output an output image when the pixel is a moving pixel; and calculating the current image and the previous image using weighted average according to the second blending value so as to generate and output the output image when the pixel is a static pixel; wherein the pixel is in a first position of the current image; and the previous image has a first previous pixel, a second previous pixel, and a third previous pixel which positions are corresponding to the first position; wherein the blending value determining unit determines a first, second, and third previous blending values for the first, second, and third previous pixels respectively; wherein the second blending value is equal to the first previous blending value when the pixel number of the first, second, and third previous pixels belonging to the static pixel is equal to or smaller than a predetermined value; and the second blending value is equal to the first blending value when the number of the first, second, and third previous pixels belonging to static pixel is greater than a predetermined value.