OpenCV 2.4.9 for Python，找不到棋盘（相机校准教程）

Question

我正在尝试根据以下this guide使用OpenCV工具校准相机。

问题是函数findChessboardCorners在我尝试的图像上找不到任何棋盘。我使用了很多 - 甚至只是简单的棋盘图案。无论如何，没有发现任何东西。

以下是代码（与上面的链接几乎相同）：

import numpy as np
import cv2
import glob

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

# prepare object points, like (0,0,0), (1,0,0), (2,0,0) ....,(6,5,0)
objp = np.zeros((6*7,3), np.float32)
objp[:,:2] = np.mgrid[0:7,0:6].T.reshape(-1,2)

# Arrays to store object points and image points from all the images.
objpoints = [] # 3d point in real world space
imgpoints = [] # 2d points in image plane.

images = glob.glob('*.png')

for fname in images:
    img = cv2.imread(fname)
    gray = cv2.cvtColor(img,cv2.COLOR_BGR2GRAY)

    # Find the chess board corners
    ret, corners = cv2.findChessboardCorners(gray, (7,6),None)

    # If found, add object points, image points (after refining them)
    if ret == True:
        objpoints.append(objp)

        corners2 = cv2.cornerSubPix(gray,corners,(11,11),(-1,-1),criteria)
        imgpoints.append(corners2)

        # Draw and display the corners
        img = cv2.drawChessboardCorners(img, (7,6), corners2,ret)
        cv2.imshow('img',img)
        cv2.waitKey(500)

cv2.destroyAllWindows()

我做的唯一改变是我从.jpg文件切换到.png文件 - 由于某种原因，函数imread无法读取jpg图像（这是其他主题的另一个奇怪问题）。

提前感谢您的建议！

图片参考：

Answer 1

对于可能会走这条路的其他Python新手。工作代码：

import numpy as np
import cv2
import glob

# termination criteria
criteria = (cv2.TERM_CRITERIA_EPS + cv2.TERM_CRITERIA_MAX_ITER, 30, 0.001)
# Arrays to store object points and image points from all the images.
imgpoints = [] # 2d points in image plane.
images = glob.glob('*.png')

for fname in images:
    img = cv2.imread(fname)
    gray = cv2.cvtColor(img,cv2.COLOR_BGR2GRAY)
    ret = False
    # Find the chess board corners
    ret, corners = cv2.findChessboardCorners(gray, (7,7))
    # If found, add object points, image points (after refining them)
    if ret == True:
        cv2.cornerSubPix(gray, corners, (11,11), (-1,-1), criteria)
        imgpoints.append(corners)
        # Draw and display the corners
        cv2.drawChessboardCorners(img, (7,7), corners, ret)
        cv2.imshow('img',img)
        cv2.waitKey(0)
cv2.destroyAllWindows()

两个要点：

1. 您必须仔细计算您的图案尺寸。 （7,7）适用于通常的棋盘。

2. 行img = cv2.drawChessboardCorners(img, (7,6), corners2,ret)不起作用，您必须将其更改为cv2.drawChessboardCorners(img, (7,6), corners2,ret)（函数不返回图像）。

感谢AldurDisciple！