ABSTRACT
This chapter reviews some of the common edge detection methods. A hard edge exists when the change is very abrupt perhaps only 2 or 3 pixels wide. A soft edge exists when the transition from bright to dark takes several pixels. A slightly more sophisticated method of edge enhancement is the Sobel filter. This process is similar to the previous except that shift operations are replaced by small kernel correlations. Each of the Sobel filters are on-center off-surround shaped. In the shift method, the edge value of a pixel was determined by the subtraction of just two pixels. In the Sobel method, the value was determined by the small kernel which included values from nine pixels. The method in this section is similar in nature, but there are more pixels involved in the determination of the edge value of a single pixel.
