OpenCV Tutorials —— Camera calibration with square chessboard

获取摄像机内部参数矩阵和摄像机畸变参数

Test data: use images in your data/chess folder.

1. 1，Compile opencv with samples by setting BUILD_EXAMPLES to ON in cmake configuration.
2. 2，Go to bin folder and use imagelist_creator to create an XML/YAML list of your images.
3. 3，Then, run calibration sample to get camera parameters. Use square size equal to 3cm.

获取到的摄像机参数信息存放在XML /YAML 文件中，然后对失真图像进行矫正

Test data: use chess_test*.jpg images from your data folder.

1. 1，Create an empty console project. Load a test image:

   Mat img = imread(argv[1], CV_LOAD_IMAGE_GRAYSCALE);

2. 2，Detect a chessboard in this image using findChessboard function.

3. bool found = findChessboardCorners( img, boardSize, ptvec, CV_CALIB_CB_ADAPTIVE_THRESH );

4. 3，Now, write a function that generates a vector<Point3f> array of 3d coordinates of a chessboard in any coordinate system. For simplicity, let us choose a system such that one of the chessboard corners is in the origin and the board is in the plane z = 0.
5. 4，Read camera parameters from XML/YAML file:

6. FileStorage fs(filename, FileStorage::READ);
   Mat intrinsics, distortion;
   fs["camera_matrix"] >> intrinsics;
   fs["distortion_coefficients"] >> distortion;

7. 5，Now we are ready to find chessboard pose by running solvePnP:

   vector<Point3f> boardPoints;
   // fill the array
   ...
   
   solvePnP(Mat(boardPoints), Mat(foundBoardCorners), cameraMatrix,
                        distCoeffs, rvec, tvec, false);

8. Calculate reprojection error like it is done in calibration sample (see opencv/samples/cpp/calibration.cpp, function computeReprojectionErrors).