Camera calibration with OpenCV - findChessboardCorners returns false

Question

I try to calibrate my camera. I run some example but all of them don't find corners of chess board. Finally, I use this question's code, but it can't find corners.There is a image below. I use it to find corners.

I find a command on web for this problem.It says that board_sz has to hold the number of inner corners, not the number of squares. board_sz is a 2-dimensional object.I don't understand that how can I use it to hold the number of inner corner except h*w.

I give w = 9,h = 7

Edit 1 ** **Code :

#include <cv.h>
#include <highgui.h>
#include <vector>
#include <stdlib.h>
#include <stdio.h>

using namespace cv;
using namespace std;

int main()
{
int numBoards = 0;
int numCornersHor;
int numCornersVer;

printf("Enter number of corners along width: ");
scanf("%d", &numCornersHor);

printf("Enter number of corners along height: ");
scanf("%d", &numCornersVer);

printf("Enter number of boards: ");
scanf("%d", &numBoards);

int numSquares = numCornersHor * numCornersVer;
Size board_sz = Size(numCornersHor, numCornersVer);
VideoCapture capture = VideoCapture(0);

vector<vector<Point3d>> object_points;
vector<vector<Point2d>> image_points;

vector<Point2d> corners;
int successes=0;

Mat image;
Mat gray_image;
capture >> image;

vector<Point3d> obj;
for(int j=0;j<numSquares;j++)
    obj.push_back(Point3d(j/numCornersHor, j%numCornersHor, 0.0f));

while(successes<numBoards)
{
    cvtColor(image, gray_image, CV_BGR2GRAY);

    bool found = findChessboardCorners(image, board_sz, corners, CV_CALIB_CB_ADAPTIVE_THRESH | CV_CALIB_CB_FILTER_QUADS);

    if(found)
    {
        cornerSubPix(gray_image, corners, Size(11, 11), Size(-1, -1), TermCriteria(CV_TERMCRIT_EPS | CV_TERMCRIT_ITER, 30, 0.1));
        drawChessboardCorners(gray_image, board_sz, corners, found);
    }

    imshow("win1", image);
    imshow("win2", gray_image);

    capture >> image;

    int key = waitKey(1);

    if(key==27)
        return 0;

    if(key==' ' && found!=0)
    {
        image_points.push_back(corners);
        object_points.push_back(obj);
        printf("Snap stored!\n");

        successes++;

        if(successes>=numBoards)
            break;
    }
}

Mat intrinsic = Mat(3, 3, CV_32FC1);
Mat distCoeffs;
vector<Mat> rvecs;
vector<Mat> tvecs;

intrinsic.ptr<float>(0)[0] = 1;
intrinsic.ptr<float>(1)[1] = 1;

calibrateCamera(object_points, image_points, image.size(), intrinsic, distCoeffs, rvecs, tvecs);

Mat imageUndistorted;
while(1)
{
    capture >> image;
    undistort(image, imageUndistorted, intrinsic, distCoeffs);

    imshow("win1", image);
    imshow("win2", imageUndistorted);

    waitKey(1);
}

capture.release();

return 0;
}

Image :

Answer 1

Try size (8,6). It is a bit confusing counting the squares correctly, but try and count the 'inside' corners.