FindContour OpenCV C ++

Question

I have trouble when using findContour() function from opencv. It crash and output the following error:

Here is my code:

using namespace cv;
using namespace std;

Mat src; Mat src_gray;
int thresh = 100;
int max_thresh = 255;
RNG rng(12345);

/// Function header
void thresh_callback(int, void*);

/** @function main */
int main(int argc, char** argv)
{
    src = imread("test.png");
    /// Load source image and convert it to gray
    //src = imread(argv[1], 1);

    /// Convert image to gray and blur it
    cvtColor(src, src_gray, CV_BGR2GRAY);
    blur(src_gray, src_gray, Size(3, 3));

    /// Create Window
    char* source_window = "Source";
    namedWindow(source_window, CV_WINDOW_AUTOSIZE);
    imshow(source_window, src);

    createTrackbar(" Canny thresh:", "Source", &thresh, max_thresh, thresh_callback);
    thresh_callback(0, 0);

    waitKey(0);
    return(0);
}

/** @function thresh_callback */
void thresh_callback(int, void*)
{
    Mat canny_output;
    vector<vector<Point> > contours;
    vector<Vec4i> hierarchy;

    /// Detect edges using canny
    Canny(src_gray, canny_output, thresh, thresh * 2, 3);
    /// Find contours
    findContours(canny_output, contours, hierarchy, CV_RETR_TREE, CV_CHAIN_APPROX_SIMPLE, Point(0, 0));

    /// Draw contours
    Mat drawing = Mat::zeros(canny_output.size(), CV_8UC3);
    for (int i = 0; i< contours.size(); i++)
    {
        Scalar color = Scalar(rng.uniform(0, 255), rng.uniform(0, 255), rng.uniform(0, 255));
        drawContours(drawing, contours, i, color, 2, 8, hierarchy, 0, Point());
    }

    /// Show in a window
    namedWindow("Contours", CV_WINDOW_AUTOSIZE);
    imshow("Contours", drawing);
}

All the setting is correct such as property sheet as the program can works but it crash once it done the thresh_callback functions. I use visual studio 2015 with opencv 3.0. I had tried on visual studio 2012 or try other version of opencv like 2.4.9. Unfortunately, it still not works. Hope you all can help me

Here showed my property sheet settings: 1. Debug x64 property sheet

2. Release x64 property sheet

I am able to run others image processing function such as cv::imread . Only the findContour() having errors.

Update

library path:

Answer 1

I have tested your code, I can compile it successfully against my input image (binary image of hand) and it does provide the contour of the hand. As mentioned by @Miki , you must check your linked libraries. On Eclipse IDE we have to go to: Project -> Properties -> C/C++ Build -> Settings. On the right side, make sure you are in the 'Tool Settings' tab and then head to MinGW C++ Linker -> Libraries. You must have something similar on Visual Studio, either way you still have to check the libraries you have included in your project in the project settings. You must have the following linked libraries apart from the other mandatory libraries:

1. libopencv_imgproc300
2. libopencv_highgui300

Please note that the number 300 suggests that the OpenCV version is 3.0 , I have OpenCV 3.1 thus my libraries contain the number 310 at the end eg - libopencv_imgproc310. Let me know if this helps.

Answer 2

You're linking the wrong libraries.

---

You are linking in:

C:\\opencv\\build\\x64\\ vc12 \\lib

That means you're using OpenCV compiled with vc12 compiler (Visual Studio 2013). But you're using Visual Studio 2015, so you need to link to OpenCV compiled with vc14 .

So, look if you have the folder:

C:\\opencv\\build\\x64\\ vc14 \\lib

Probably not, because OpenCV 3.0 has not the prebuild for vc14. In this case you can either:

1. Recompile OpenCV 3.0 with vc14
2. Download OpenCV 3.2 which has prebuilt binaries for x64,vc14. This is the recommended approach, since OpenCV 3.2 added some nice functions, and several bug fixes.
3. Use Visual Studio 2013 with your current libraries