1. An image sharpening method performed on a computer system, the method comprising: performing bilateral filtering processing and difference of Gaussians filtering processing on original image information to obtain first image-layer information and second image-layer information, respectively; subtracting the first image-layer information from the original image information to obtain third image-layer information; performing fusion and superimposition processing on the second image-layer information and the third image-layer information to obtain fourth image-layer information; and adding the original image information and the fourth image-layer information to obtain processed image information.