hittest.dart

double grayScaleFromPixel(img.Pixel px) {
  return (px.r + px.g + px.b) / 3;
}

bool _hitTest(img.Image? clipImage, int x1, int y1, int x2, int y2, int width,
    int height) {
  // 切り抜き画像がnullかどうか
  if (clipImage == null) {
    return false;
  }
  //中心座標
  int centerX = ((x2 - x1) / 2).toInt();
  int centerY = ((y2 - y1) / 2).toInt();
  List<double> grayScales = [
    /* 中心 */
    grayScaleFromPixel(clipImage.getPixel(centerX, centerY)),
    /* 右 */
    grayScaleFromPixel(clipImage.getPixel(centerX + 1, centerY)),
    /* 左 */
    grayScaleFromPixel(clipImage.getPixel(centerX - 1, centerY)),
    /* 下 */
    grayScaleFromPixel(clipImage.getPixel(centerX, centerY + 1)),
    /* 上 */
    grayScaleFromPixel(clipImage.getPixel(centerX, centerY - 1))
  ];
  double grayScale = grayScales.reduce((a, b) => a + b) / grayScales.length;
  Logger.info('grayScales:${grayScales.toString()}');
  Logger.info('grayScale:${grayScale.toString()}');
  if (grayScale < 128) {
    // 見つめてる
    return true;
  } else {
    // 見つめてない
    return false;
  }
}