Sharpens the image edges. Two algorithms are supplied:
usm: Sharpens with the application of a blurred copy of the image, similar to the old film
technique. Sigma controls the blur extent, radius controls the radius of the blur.
convolution: Sharpens with the application of a simple 3x3 convolution kernel,
adjustable in strength from 1 to 10 in 0.1 increments. The 0 value is no-sharpen.
The kernel used to apply the sharpening is displayed. Of note:
The algorithm that performs the convolution takes the pixels in the 3x3 area surrounding the pixel to be
modified, multiplies each by the corresponding kernel value (including the center pixel), and replaces the
pixel value with the sum of those multplications.
The matrix that produces no-change, or the 'identity matrix', has 1.0 as its center value and 0.0 for the
surrounding values.