Sharpen bitmap using Convolution

The previous exercise "Blur bitmap using Convolution". By changing the matrix of Convolution class, we can use it to sharpen bitmap.

 class Convolution {

  // matrix to sharpen image
  int[][] matrix = { { 0, -1, 0 }, { -1, 5, -1 }, { 0, -1, 0 } };
  ...