Sharpening filters are used to enhance the edges of objects and adjust the contrast and the shade characteristics. In combination with threshold they can be used as edge detectors. Sharpening or high-pass filters let high frequencies pass and reduce the lower frequencies and are extremely sensitive to shut noise.
To construct a high-pass filter the kernel coefficients should be set positive near the center of the kernel and in the outer periphery negative.
The sharpening filters are divided into the following groups:
- High Pass Filters (Uni Crisp)
- Laplacian of Gaussian / Mexican Hat filters.
Typical kernel sizes are 3x3 to 7x7 but larger kernels can also be applied.
When checking "Equal" check box the X and Y kernel size are kept equal.