compute method

@override double compute(Image image)

Implementation

@override
double compute(img.Image image) {
  final sobelX = generateSobelKernel('x');
  final sobelY = generateSobelKernel('y');

  double sum = 0;

  for (int y = 1; y < image.height - 1; y++) {
    for (int x = 1; x < image.width - 1; x++) {
      double gx = 0;
      double gy = 0;
      for (int ky = -1; ky <= 1; ky++) {
        for (int kx = -1; kx <= 1; kx++) {
          final gray = pixelToGray(image, x + kx, y + ky);
          gx += gray * sobelX[ky + 1][kx + 1];
          gy += gray * sobelY[ky + 1][kx + 1];
        }
      }
      final magnitude = gx * gx + gy * gy;
      sum += magnitude;
    }
  }
  return sum / ((image.width - 2) * (image.height - 2));
}