1. A system for applying multi-direction and multi-slope region detection to image edge enhancement, which performs the image edge enhancement on image comprised of multiple lines, where pixel (i) indicates i-th pixel of line of the image, the system comprising: a line buffer for receiving and temporarily storing the pixel (i) and neighboring pixels corresponding to the pixel (i) of the image; a region classification device, connected to the line buffer, to classify the pixel (i) into a region type, wherein the region type is one selected from a group consisting of a left flat region, a right flat region, a flat region, a short flat region, an extended region and a hill region; a left flat pixel detector, connected to the region classification device, to search the neighboring pixels of the pixel (i) for a left flat region pixel; a right flat pixel detector, connected to the region classification device, to search the neighboring pixels of the pixel (i) for a right flat region pixel; and an edge enhancer, connected to the line buffer, the region classification device, the left flat pixel detector and the right flat pixel detector, to perform edge enhancement on the pixel (i) when the pixel (i) is the extended region and the left and the right flat region pixels are included in the neighboring pixels.