OpenCv fails to find chessboard pattern on many of my images and Matlab not

Question

I am doing GoPro camera calibration with OpenCv. But findChessboardCorners return false on many of my images and Matlab not. I have tried to biniraze images to help OpenCv but it helps only in some cases. Here is example:

Here is code:

CHECKERBOARD = (6,9)
 img = cv2.imread('1.JPG') 
 gray = cv2.cvtColor(img,cv2.COLOR_BGR2GRAY)

 ret, corners = cv2.findChessboardCorners(gray, CHECKERBOARD, cv2.CALIB_CB_ADAPTIVE_THRESH+cv2.CALIB_CB_FAST_CHECK+cv2.CALIB_CB_NORMALIZE_IMAGE) 
 print(ret)

I have tried different flags. OpenCv fails and matlab not. Any hint?

Answer 1

Resizing the image seems to work.

Code Sample:

import cv2
import numpy as np

CHECKERBOARD = (6,9)

img = cv2.imread("Q2l11.jpg")
img = cv2.resize(img,(int(400),int(400)))


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

ret, corners = cv2.findChessboardCorners(gray, CHECKERBOARD, cv2.CALIB_CB_ADAPTIVE_THRESH+cv2.CALIB_CB_FAST_CHECK+cv2.CALIB_CB_NORMALIZE_IMAGE)
print(corners)
#print(ret)

corners = np.int0(corners)

for i in corners:
    x,y = i.ravel()
    cv2.circle(img,(x,y),3,(0,0,255),-1)

cv2.imshow('Corners',img)

cv2.waitKey(0)

Result: