computeBlurScore static method

double computeBlurScore(Uint8List gray, int width, int height)

Calculates Laplacian variance sharpness score for blur detection. Inspired by OpenCV Laplacian variance algorithm.

Implementation

static double computeBlurScore(Uint8List gray, int width, int height) {
  if (gray.length < width * height || width < 3 || height < 3) return 0.0;

  double sum = 0.0;
  double sumSq = 0.0;
  int count = 0;

  // 3x3 Discrete Laplacian Kernel:
  // [  0,  1,  0 ]
  // [  1, -4,  1 ]
  // [  0,  1,  0 ]
  final stride = width;
  for (int y = 1; y < height - 1; y += 2) {
    final row = y * stride;
    for (int x = 1; x < width - 1; x += 2) {
      final idx = row + x;
      final lap = gray[idx - stride] +
          gray[idx - 1] +
          gray[idx + 1] +
          gray[idx + stride] -
          (4 * gray[idx]);
      final val = lap.toDouble();
      sum += val;
      sumSq += val * val;
      count++;
    }
  }

  if (count == 0) return 0.0;
  final mean = sum / count;
  final variance = (sumSq / count) - (mean * mean);
  return math.max(0.0, variance);
}