Abort trap:6 problem with findchessboard

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I'm new on this forum. I'd like to ask you a question that has been annoying me all this day. the problem is that i don't find anything on internet about it. At the university we have to do this: Write a program that: -Loads the checkerboard images. ( these imagines are in a folder provided by the professor, they represent some pictures (15) taken by a Huawei smartphone of a chessboard). -Detects the checkerboard intersections in each image. The OpenCV function you need is cv::findChessboardCorners() (optional: consider to use the cv::cornerSubPix() function to refine the corner detections).

I'm writing it with Xcode ( c++) with opencv 3.4.5 on a Macbook.

The problem is that at the instruction "findChessboardCorners" it gets me an error. I really don't understand what causes it, the problem is " abort trap: 6. Can Someone help me?

Thank you very much.

What I have tried:

C++

#include <sstream>
#include <iostream>
#include <opencv2/core.hpp>
#include <opencv2/calib3d/calib3d.hpp>
#include <opencv2/highgui.hpp>
#include <opencv2/imgproc.hpp>


#define points_per_row 12
#define points_per_colum 8
using namespace cv;
using namespace std;


int main(int argc, const char * argv[]) {
    //read the file
    stringstream sst;
    vector<Mat> imagesArray;
    vector<Point2f> centers; //this will be filled by the detected centers
    Size patternSize = Size(11, 7); //2nd parameter FindchessCorners
    bool patternfound = false; //result of findChessboardCorners

    cout << "flag1 "<< endl;
    for(int i = 1; i < 16; i++){
        sst << "img" << i << ".jpg";
        cout << sst.str() << endl;
        imagesArray.push_back(imread(sst.str())); // putting into an array
        cout << "flag2" << endl;
    }//for
    //PUNTO 2: individuation of the corners of every image
    for(int i = 0 ; i <=15 ; i++){
        cout << "flag3" << endl;
        patternfound = findChessboardCorners(imagesArray[i] , patternSize , centers);
        if(patternfound){
            cout << "pattern found:"<< patternSize << endl;
            cout << "centroids: " << centers << endl;
            cout << "centroids array size: " << centers.size() << endl;
        for(int j = 0; j < centers.size(); j++)
                cout << centers[j] << endl;
        }
    }//for

return 0;
}

Posted 22-Mar-19 8:30am

Member 14192637

Updated 23-Mar-19 2:34am

Richard MacCutchan

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Rick York · Answer 1 · 2019-03-22T16:29:00

The problem is in the for loops. You stated there are fifteen images. Since array indexes start with zero, the fifteenth image will be index fourteen but your for loop goes out to fifteen. A better way to do this would be to define a constant :

C++

const int ImageCount = 15;

// and write the for loops like this :

for( int i = 0; i < ImageCount; ++i )
{
    sst << "img" << i + 1 << ".jpg";   // first image is 1

    // rest of code goes here
}

for( int i = 0 ; i < ImageCount ; i++)
{
    patternfound = findChessboardCorners( imagesArray[i] , patternSize , centers );

    // rest of code goes here
}

This should work better for you

Member 14192637 · Answer 2 · 2019-03-22T22:51:00

Hi. First of all, thank you for answering. I followed your valuable advice(with a little modification, but that's the point), but the problem doesn't change. here the piece of the code correct:

for(int i = 0 ; i < imagesArray.size(); i++){
                        cout << "flag3" << endl;
                        patternfound = findChessboardCorners(imagesArray[i] , patternSize , centers);
                        if(patternfound){
                            cout << "pattern found:"<< patternSize << endl;
                            cout << "centroids: " << centers << endl;
                            cout << "centroids array size: " << centers.size() << endl;
                        for(int j = 0; j < centers.size(); j++)
                                cout << centers[j] << endl;
                        }//if
                    }//for

But still I get the same error when I compile:

libc++abi.dylib: terminating with uncaught exception of type cv::Exception: OpenCV(3.4.5) /tmp/opencv@3-20190117-71360-ynjwgu/opencv-3.4.5/modules/core/src/matrix.cpp:757: error: (-215:Assertion failed) dims <= 2 && step[0] > 0 in function 'locateROI'

Abort trap: 6

Abort trap:6 problem with findchessboard

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