undistort.py

#!/usr/bin/env python2
# coding: utf-8

'''
Camera calibration. 
Print ChessBoard.pdf
Take picture of ChessBoard.
Be careful to make the picture clear and take picture with ChessBoard placed at any where.
'''

import cv2
import glob
import numpy as np

# 找棋盘格角点
# 阈值
criteria = (cv2.TERM_CRITERIA_EPS + cv2.TERM_CRITERIA_MAX_ITER, 30, 0.001)
#棋盘格模板规格
w = 9
h = 6
# 世界坐标系中的棋盘格点,例如(0,0,0), (1,0,0), (2,0,0) ....,(8,5,0)，去掉Z坐标，记为二维矩阵
objp = np.zeros((w*h,3), np.float32)
objp[:,:2] = np.mgrid[0:w,0:h].T.reshape(-1,2)
# 储存棋盘格角点的世界坐标和图像坐标对
objpoints = [] # 在世界坐标系中的三维点
imgpoints = [] # 在图像平面的二维点

images = glob.glob('/Users/apple/Documents/Atom/undistort_photo/*.png')
for fname in images:
    img = cv2.imread(fname)
    gray = cv2.cvtColor(img,cv2.COLOR_BGR2GRAY)
    # 找到棋盘格角点
    ret, corners = cv2.findChessboardCorners(gray, (w,h),None)
    # 如果找到足够点对，将其存储起来
    if ret == True:
        cv2.cornerSubPix(gray,corners,(11,11),(-1,-1),criteria)
        objpoints.append(objp)
        imgpoints.append(corners)
        # 将角点在图像上显示
        cv2.drawChessboardCorners(img, (w,h), corners, ret)
        cv2.imshow('findCorners',img)
        cv2.waitKey(1)
cv2.destroyAllWindows()

# 标定
ret, mtx, dist, rvecs, tvecs = cv2.calibrateCamera(objpoints, imgpoints, gray.shape[::-1], None, None)
print(mtx,dist)

# 去畸变
i = 0
for fname in images:
    i += 1
    img2 = cv2.imread(fname)
    h, w = img2.shape[:2]
    newcameramtx, roi = cv2.getOptimalNewCameraMatrix(mtx, dist, (w, h), 0, (w, h))  # 自由比例参数
    dst = cv2.undistort(img2, mtx, dist, None, newcameramtx)
    # 根据前面ROI区域裁剪图片
    # x,y,w,h = roi
    # dst = dst[y:y+h, x:x+w]
    cv2.imwrite('/Users/apple/Documents/Atom/undistort_photo/result/calibresult%d.png'%i, dst)


# 反投影误差
total_error = 0
for i in xrange(len(objpoints)):
    imgpoints2, _ = cv2.projectPoints(objpoints[i], rvecs[i], tvecs[i], mtx, dist)
    error = cv2.norm(imgpoints[i],imgpoints2, cv2.NORM_L2)/len(imgpoints2)
    total_error += error
print "total error: ", total_error/len(objpoints)