docs: public static int Minimum(ImageSource fastBitmap, int startX, int startY, int width, int height) {
          int min = 255;
          if (fastBitmap.isGrayscale()) {
              for (int i = startX; i < height; i++) {
                  for (int j = startY; j < width; j++) {
                      int gray = fastBitmap.getRGB(j, i);
                      if (gray < min) {
                          min = gray;
                      }
                  }
              }
          } else {
              for (int i = startX; i < height; i++) {
                  for (int j = startY; j < width; j++) {
                      int gray = fastBitmap.getG(j, i);
                      if (gray < min) {
                          min = gray;
                      }
                  }
              }
          }
          return min;
      }