In this paper, we propose an automatic and efficient method to enhance edge sharpness of images. Starting from an image with blur edges, we improve the edges using transformed Heaviside functions for better visualization. In addition, we provide an efficient method to directly compute the scaling and shifting factors of the transformed Heaviside functions, so that blur edges can be improved accurately. Experimental results show that the proposed method is fast and can get sharper image edges than some recent state-of-the-art edge enhancement methods. We also apply the edge sharpening method to image super-resolution and obtained promising results.