1. An artifact reduction method, comprising: scaling down a resolution of a current original image frame from a first resolution to a second resolution to obtain a current low-resolution image frame, wherein the current original image frame and the current low-resolution image frame comprise a first plurality of pixels and a second plurality of pixels, respectively; performing an artifact detection to the current low-resolution image frame to obtain a plurality of low-resolution weights, wherein the low-resolution weights are respectively corresponding to the second plurality of pixels in the current low-resolution image frame; scaling up a number of the low-resolution weights to generate a plurality of high-resolution weights, wherein the high-resolution weights are respectively corresponding to the first plurality of pixels in the current original image frame; and performing a temporal noise reduction to the current original image frame by using the high-resolution weights for reducing artifact of the current original image frame and obtaining an adjusted image frame.