1. An image enhancement method, adapted to an image processing apparatus, the image enhancement method comprising: obtaining an input image, wherein the input image has a plurality of intensity components; correcting the input image according to a gamma curve; enhancing sharpness of the corrected input image based on an edge detection operator and a weight value; and obtaining an output image suitable for a display panel based on the enhanced input image, wherein when the corrected input image is a normal image, the edge detection operator is shown as 1 9 × [ - 2 - 2 - 2 - 2 25 - 2 - 2 - 2 - 2 ] , when image content of the corrected input image includes background noise, the edge detection operator is shown as 1 8 × [ - 1 - 1 - 1 - 1 16 - 1 - 1 - 1 - 1 ] .