Python opencv 检测棋盘

我正在尝试获取棋盘图案的角点，并认为我可以将 openCV 与cv2.findChessboardCorners.

但是，我找不到传递给该函数的良好参数，以便它成功检测棋盘。我认为该图像适合此功能。如果不是，我不知道我应该做什么预处理。

这是我的代码：

import numpy as np
import cv2
import glob
import sys
import os

nline = 4
ncol = 4 

img = cv2.imread(glob.glob('*.jpg')[0])

## termination criteria
criteria = (cv2.TERM_CRITERIA_EPS + cv2.TERM_CRITERIA_MAX_ITER, 30, 0.001)

## processing
gray = cv2.cvtColor(img, cv2.COLOR_BGR2GRAY)

# Find the chessboard corners
ret, corners = cv2.findChessboardCorners(gray, (nline, ncol), None)
corners2 = cv2.cornerSubPix(gray, corners, (11, 11), (-1, -1), criteria)

and this is the image :

我尝试过各种尺寸的图案给他，因为我认为4*4的图案会更容易找到，但事实并非如此。

EDIT : Actually using the appropriated number of lines and columns its works :

However, it doesn't for these ones which are not so different from the first one ... 11 lines, for 8 or 9 columns, tried both.

Or this one : which is 13*9.

如何处理此类图像？

参数nline and ncol必须准确，（行数 -1，列数 -1）

nline = 11
ncol = 9