for i in range(int(h / 3), int(h * 2 / 3), 50):
    last_pixel = im_pixel[0, i]
    for j in range(1, w):
      pixel = im_pixel[j, i]
      # 不是纯色的线，则记录 scan_start_y 的值，准备跳出循环
      if pixel[0] != last_pixel[0] or pixel[1] != last_pixel[1] or pixel[2] != last_pixel[2]:
        scan_start_y = i - 50
        break
    if scan_start_y:
      break

# 查找棋子坐标
  # piece_x_sum 横坐标总量 piece_x_c 点的个数 piece_y_max 纵坐标最大值
  # 从 scan_start_y 开始往下扫描，棋子应位于屏幕上半部分，这里暂定不超过 2/3
  for i in range(scan_start_y, int(h * 2 / 3)):
    for j in range(scan_x_border, w - scan_x_border): # 横坐标方面也减少了一部分扫描开销
      pixel = im_pixel[j, i]
      # 根据棋子的最低行的颜色判断，找最后一行那些点的平均值，这个颜色这样应该 OK，暂时不提出来
      if (50 < pixel[0] < 60) and (53 < pixel[1] < 63) and (95 < pixel[2] < 110):
        piece_x_sum += j
        piece_x_c += 1
        piece_y_max = max(i, piece_y_max)

  if not all((piece_x_sum, piece_x_c)):
    return 0, 0, 0, 0
  # 平均横坐标
  piece_x = int(piece_x_sum / piece_x_c)
  # 纵坐标最大值-底座一半的高度
  piece_y = piece_y_max - piece_base_height_1_2 # 上移棋子底盘高度的一半

# 寻找最高的棋盘
  # 棋盘不会和棋子在同一侧
  # 限制棋盘扫描的横坐标，避免音符 bug
  if piece_x < w / 2:
    board_x_start = piece_x
    board_x_end = w
  else:
    board_x_start = 0
    board_x_end = piece_x
  for i in range(int(h / 3), int(h * 2 / 3)):
    last_pixel = im_pixel[0, i]
    if board_x or board_y:
      break
    board_x_sum = 0
    board_x_c = 0
    for j in range(int(board_x_start), int(board_x_end)):
      pixel = im_pixel[j, i]
      # 下一个棋盘紧贴着棋子
      # 修掉脑袋比下一个小格子还高的情况的 bug
      if abs(j - piece_x) < piece_body_width:
        continue
      # 修掉圆顶的时候一条线导致的小 bug，这个颜色判断应该 OK，暂时不提出来
      if abs(pixel[0] - last_pixel[0]) + abs(pixel[1] - last_pixel[1]) + abs(pixel[2] - last_pixel[2]) > 10:
        board_x_sum += j
        board_x_c += 1
    if board_x_sum:
      # 最高棋盘的平均横坐标
      board_x = board_x_sum / board_x_c
  last_pixel = im_pixel[board_x, i]