Image Processing in C#: Part 8 - Sharpening an Image
Sharpening an image is merely the inverse of what we did to blur the image. It also uses the convolution function, which you can read in my post about smoothing using convolution.
Here we supply a convolution matrix set up as follows:
| 0 | -2 | 0 |
| -2 | 11 | -2 |
| 0 | -2 | 0 |
Here our weighting factor would total 3, since the negative numbers get subtracted from the weighting total.
public void ApplySharpen(double weight)
{
ConvolutionMatrix matrix = new ConvolutionMatrix(3);
matrix.SetAll(1);
matrix.Matrix[0, 0] = 0;
matrix.Matrix[1, 0] = -2;
matrix.Matrix[2, 0] = 0;
matrix.Matrix[0, 1] = -2;
matrix.Matrix[1, 1] = weight;
matrix.Matrix[2, 1] = -2;
matrix.Matrix[0, 2] = 0;
matrix.Matrix[1, 2] = -2;
matrix.Matrix[2, 2] = 0;
matrix.Factor = weight - 8;
bitmapImage = Convolution3x3(bitmapImage, matrix);
}The full source used in the series is available from https://github.com/sjmeunier/image-processor.
Originally posted on my old blog, Smoky Cogs, on 19 Nov 2009