This is the next post in our series of convolution filter examples. We examine one method of image sharpening using the unsharp sharpening mask (unsharp filter). You can think of sharpening as the opposite of blurring. The previous post showed how blurring was like taking an average. The process reduces the size of the differences between neighbours, causing a blurring effect.
Sharpening on the other hand, emphasises differences between neighbouring pixel values, increasing the contrast between pixels.