calib_w_pictures.cpp

#include <opencv2/opencv.hpp>
#include <opencv2/calib3d/calib3d.hpp>
#include <opencv2/highgui/highgui.hpp>
#include <opencv2/imgproc/imgproc.hpp>
#include <stdio.h>
#include <iostream>
 
// Defining the dimensions of checkerboard
int CHECKERBOARD[2]{11,7}; 

int main()
{
    // Creating vector to store vectors of 3D points for each checkerboard image
    std::vector<std::vector<cv::Point3f> > objpoints;

    // Creating vector to store vectors of 2D points for each checkerboard image
    std::vector<std::vector<cv::Point2f> > imgpoints;

    // Defining the world coordinates for 3D points
    std::vector<cv::Point3f> objp;
    for(int i{0}; i<CHECKERBOARD[1]; i++)
    {
      for(int j{0}; j<CHECKERBOARD[0]; j++)
        objp.push_back(cv::Point3f(j,i,0));
    }


    // Extracting path of individual image stored in a given directory
    std::vector<cv::String> images;
    // Path of the folder containing checkerboard images
    std::string path = "./images/*.png";

    cv::glob(path, images);

    cv::Mat frame, gray;
    // vector to store the pixel coordinates of detected checker board corners
    std::vector<cv::Point2f> corner_pts;
    bool success;

    // Looping over all the images in the directory
    for(int i{0}; i<images.size(); i++)
    {
      frame = cv::imread(images[i]);
      cv::cvtColor(frame,gray,cv::COLOR_BGR2GRAY);

      cv::imshow("Image_raw",gray);

      // Finding checker board corners
      // If desired number of corners are found in the image then success = true
      success = cv::findChessboardCorners(gray, cv::Size(CHECKERBOARD[0], CHECKERBOARD[1]), corner_pts, cv::CALIB_CB_ADAPTIVE_THRESH | cv::CALIB_CB_FAST_CHECK | cv::CALIB_CB_NORMALIZE_IMAGE);      

    /*
     * If desired number of corner are detected,
     * we refine the pixel coordinates and display
     * them on the images of checker board
     */
    if(success)
    {
      cv::TermCriteria criteria(cv::TermCriteria::MAX_ITER | cv::TermCriteria::EPS, 30, 0.001);

      // refining pixel coordinates for given 2d points.
      cv::cornerSubPix(gray,corner_pts,cv::Size(11,11), cv::Size(-1,-1),criteria);
       
      // Displaying the detected corner points on the checker board
      cv::drawChessboardCorners(frame, cv::Size(CHECKERBOARD[0], CHECKERBOARD[1]), corner_pts, success);
       
      objpoints.push_back(objp);
      imgpoints.push_back(corner_pts);
    }
 
    cv::imshow("Image",frame);
    char c = (char)cv::waitKey(333);
    if (c == 27)
    {
      std::cout << "User stopped calibration." << std::endl;
      break;
    }
  }
 
  cv::destroyAllWindows();
 
  cv::Mat cameraMatrix,distCoeffs,R,T;
 
  /*
   * Performing camera calibration by 
   * passing the value of known 3D points (objpoints)
   * and corresponding pixel coordinates of the 
   * detected corners (imgpoints)
  */
  cv::calibrateCamera(objpoints, imgpoints, cv::Size(gray.rows,gray.cols), cameraMatrix, distCoeffs, R, T);
 
  std::cout << "\n\n- - - CALIBRATION RESULTS - - -"<< std::endl;
  std::cout << "\ncameraMatrix :\n" << cameraMatrix << std::endl;
  std::cout << "\ndistCoeffs :\n" << distCoeffs << std::endl;
  std::cout << "\nRotation vector :\n" << R << std::endl;
  std::cout << "\nTranslation vector :\n" << T << std::endl;
 
  return 0;
}