Up to now, we have been using filters that subtract details from the images. There is a way to do the opposite, which is to highlight details. This can be done using the edge enhancement kernels available, or the unsharp kernel provided by the fspecial function. The second option is quite straightforward and involves only filtering the image using the contrast enhancement filter. The first option though, is a little trickier and demands an understanding of the edge enhancement filtering results. Let's first try to understand these results, using an example.