1. A method for pre-processing image data, comprising: storing an image in a memory module; coupling a pre-processing module to the memory module to form a processing loop, wherein the pre-processing module is operatively connected to a plurality of pre-processing parameter sets; and conveying the image from the memory module to the pre-processing module via the loop so as to allow the pre-processing module to pre-process the image in multiple times, wherein the parameter sets used for pre-processing in at least some of the multiple times are different from the parameter sets used for pre-processing in other of the multiple times.