1. An adaptive image sharpening method, for generating a sharpened image area corresponding to an original image area, the original image area including a plurality of original pixel values, the method comprising: blurring the original image area to generate a plurality of blurred pixel values corresponding to the plurality of original pixel values respectively; calculating a plurality of characteristic values corresponding to the plurality of original pixel values respectively; statistically analyzing the plurality of characteristic values to generate a plurality of weighting values corresponding to the plurality of original pixel values respectively; and generating a plurality of sharpened pixel values according to the plurality of original pixel values, the plurality of weighting values, and the plurality of blurred pixel values; wherein the plurality of sharpened pixel values constitute the sharpened image area.