calibrate.cpp

#include <opencv2/opencv.hpp>
#include <opencv2/calib3d/calib3d.hpp>
#include <opencv2/highgui/highgui.hpp>
#include <opencv2/imgproc/imgproc.hpp>
#include <opencv2/core/types_c.h>
#include <opencv2/videoio/videoio_c.h>
#include <stdio.h>
#include <iostream>

int CHECKERBOARD[2]{6,9};
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 = "./imgs/left/*.jpg";

    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);
        success = cv::findChessboardCorners(gray, cv::Size(CHECKERBOARD[0], CHECKERBOARD[1]), corner_pts, CALIB_CB_ADAPTIVE_THRESH | CALIB_CB_NORMALIZE_IMAGE);

        if(success)
        {
            cv::TermCriteria criteria(CV_TERMCRIT_EPS | CV_TERMCRIT_ITER, 30, 0.001);
            
            cv::cornerSubPix(gray,corner_pts,cv::Size(11,11), cv::Size(-1,-1),criteria);
            
            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);
        cv::waitKey(0);
    }

    cv::destroyAllWindows();

    cv::Mat cameraMatrix,distCoeffs,R,T;

    cv::calibrateCamera(objpoints, imgpoints, cv::Size(gray.rows, gray.cols), cameraMatrix, distCoeffs, R, T);

    std::cout << "cameraMatrix : " << cameraMatrix << std::endl;
    std::cout << "distCoeffs : " << distCoeffs << std::endl;
    std::cout << "Rotation vector : " << R << std::endl;
    std::cout << "Translation vector : " << T << std::endl;
}