call of overloaded ‘Point_(cv::Point2f&)’ is ambiguous

Question

I am working on some example code for OpenCV2 & C++ and I got stuck. Compiler (MinGW, g++ 4.7.2 on Win7) says that call of overloaded ‘Point_(cv::Point2f&)’ is ambiguous but I can't find exatcly what is wrong. Here is error:

18:09:33 **** Incremental Build of configuration Debug for project Blobs ****
Info: Internal Builder is used for build
g++ "-IC:\\OpenCV246PC\\build\\include" -O0 -g3 -Wall -c -fmessage-length=0 -o blobs.o "..\\blobs.cpp" 
..\blobs.cpp: In function ‘int main()’:
..\blobs.cpp:65:21: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
..\blobs.cpp:65:43: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
..\blobs.cpp:99:37: error: call of overloaded ‘Point_(cv::Point2f&)’ is ambiguous
..\blobs.cpp:99:37: note: candidates are:
In file included from ..\blobs.cpp:20:0:
C:\OpenCV246PC\build\include/opencv2/core/core.hpp:740:5: note: cv::Point_<_Tp>::Point_(const CvPoint2D32f&) [with _Tp = int; CvPoint2D32f = CvPoint2D32f]
C:\OpenCV246PC\build\include/opencv2/core/core.hpp:739:5: note: cv::Point_<_Tp>::Point_(const CvPoint&) [with _Tp = int; CvPoint = CvPoint]
C:\OpenCV246PC\build\include/opencv2/core/core.hpp:738:5: note: cv::Point_<_Tp>::Point_(const cv::Point_<_Tp>&) [with _Tp = int; cv::Point_<_Tp> = cv::Point_<int>]

// ERROR IS HERE
// It god mixed up when I pasted, so line number is not the one compiler complains.
    cv::circle(result, cv::Point(center), static_cast<int>(radius), cv::Scalar(0), 2);

And here is code:

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

int main()
{
    // Read input binary image
    cv::Mat image = cv::imread("binaryGroup.bmp", 0);
    if (!image.data)
        return 0;

    cv::namedWindow("Binary Image");
    cv::imshow("Binary Image", image);

    // Get the contours of the connected components
    std::vector<std::vector<cv::Point> > contours;
    cv::findContours(image, contours, // a vector of contours
            CV_RETR_EXTERNAL, // retrieve the external contours
            CV_CHAIN_APPROX_NONE); // retrieve all pixels of each contours

    // Print contours' length
    std::cout << "Contours: " << contours.size() << std::endl;
    std::vector<std::vector<cv::Point> >::const_iterator itContours = contours.begin();
    for (; itContours != contours.end(); ++itContours)
    {

        std::cout << "Size: " << itContours->size() << std::endl;
    }

    // draw black contours on white image
    cv::Mat result(image.size(), CV_8U, cv::Scalar(255));
    cv::drawContours(result, contours, -1, // draw all contours
            cv::Scalar(0), // in black
            2); // with a thickness of 2

    cv::namedWindow("Contours");
    cv::imshow("Contours", result);

    // Eliminate too short or too long contours
    int cmin = 100;  // minimum contour length
    int cmax = 1000; // maximum contour length
    std::vector<std::vector<cv::Point> >::iterator itc = contours.begin();
    while (itc != contours.end())
    {

        if (itc->size() < cmin || itc->size() > cmax)
            itc = contours.erase(itc);
        else
            ++itc;
    }

    // draw contours on the original image
    cv::Mat original = cv::imread("group.jpg");
    cv::drawContours(original, contours, -1, // draw all contours
            cv::Scalar(255, 255, 255), // in white
            2); // with a thickness of 2

    cv::namedWindow("Contours on Animals");
    cv::imshow("Contours on Animals", original);

    // Let's now draw black contours on white image
    result.setTo(cv::Scalar(255));
    cv::drawContours(result, contours, -1, // draw all contours
            cv::Scalar(0), // in black
            1); // with a thickness of 1
    image = cv::imread("binaryGroup.bmp", 0);

    // testing the bounding box
    cv::Rect r0 = cv::boundingRect(cv::Mat(contours[0]));
    cv::rectangle(result, r0, cv::Scalar(0), 2);

    // testing the enclosing circle
    float radius;
    cv::Point2f center;

    // http://opencv.willowgarage.com/documentation/cpp/structural_analysis_and_shape_descriptors.html#cv-minenclosingcircle
    // void minEnclosingCircle(const Mat& points, Point2f& center, float& radius)
    cv::minEnclosingCircle(cv::Mat(contours[1]), center, radius);

    // http://opencv.willowgarage.com/documentation/cpp/drawing_functions.html#cv-circle
    // void circle(Mat& img, Point center, int radius, const Scalar& color, int thickness=1, int lineType=8, int shift=0)

// ERROR IS HERE
        cv::circle(result, cv::Point(center), static_cast<int>(radius), cv::Scalar(0), 2); // <--- ERROR IS HERE

//  cv::RotatedRect rrect= cv::fitEllipse(cv::Mat(contours[1]));
//  cv::ellipse(result,rrect,cv::Scalar(0),2);

    // testing the approximate polygon
    std::vector<cv::Point> poly;
    cv::approxPolyDP(cv::Mat(contours[2]), poly, 5, true);

    std::cout << "Polygon size: " << poly.size() << std::endl;

    // Iterate over each segment and draw it
    std::vector<cv::Point>::const_iterator itp = poly.begin();
    while (itp != (poly.end() - 1))
    {
        cv::line(result, *itp, *(itp + 1), cv::Scalar(0), 2);
        ++itp;
    }
    // last point linked to first point
    cv::line(result, *(poly.begin()), *(poly.end() - 1), cv::Scalar(20), 2);

    // testing the convex hull
    std::vector<cv::Point> hull;
    cv::convexHull(cv::Mat(contours[3]), hull);

    // Iterate over each segment and draw it
    std::vector<cv::Point>::const_iterator it = hull.begin();
    while (it != (hull.end() - 1))
    {
        cv::line(result, *it, *(it + 1), cv::Scalar(0), 2);
        ++it;
    }
    // last point linked to first point
    cv::line(result, *(hull.begin()), *(hull.end() - 1), cv::Scalar(20), 2);

    // testing the moments

    // iterate over all contours
    itc = contours.begin();
    while (itc != contours.end())
    {

        // compute all moments
        cv::Moments mom = cv::moments(cv::Mat(*itc++));

        // draw mass center
        cv::circle(result,
        // position of mass center converted to integer
                cv::Point(mom.m10 / mom.m00, mom.m01 / mom.m00), 2, cv::Scalar(0), 2); // draw black dot
    }

    cv::namedWindow("Some Shape descriptors");
    cv::imshow("Some Shape descriptors", result);

    // New call to findContours but with CV_RETR_LIST flag
    image = cv::imread("binaryGroup.bmp", 0);

    // Get the contours of the connected components
    cv::findContours(image, contours, // a vector of contours
            CV_RETR_LIST, // retrieve the external and internal contours
            CV_CHAIN_APPROX_NONE); // retrieve all pixels of each contours

    // draw black contours on white image
    result.setTo(cv::Scalar(255));
    cv::drawContours(result, contours, -1, // draw all contours
            cv::Scalar(0), // in black
            2); // with a thickness of 2
    cv::namedWindow("All Contours");
    cv::imshow("All Contours", result);

    cv::waitKey();
    return 0;
}

What I am doing wrong?

EDIT: I would like that some of those who gave me down vote try to resolve this. This is not the only question of this type here, yet mine was down voted three times already?

Moreover, this is example from book written by professor from Canada ( http://www.laganiere.name/opencvCookbook/ ), who teaches both OpenCV, am I supposed to be better at this than him? Should I been ashamed that I ask this? I a novice both at C++ and OpenCV? Should I ask on ten other forums and then, only then if I don't find answer ask here on Stackoverflow?

Moreover, I am not lazy, I helped this man by rewriting his code ( OpenCV: record footage in one window and Display the same video in 2nd window but with contours only ). I helped to someone who knows less than me. But, in this case I just don't know how to solve this issue in this code and yet within 30 minutes I got three down votes?

UPDATE: As pointed to me by OpenCV community, actually it should be allowed to convert Point to Point2f and vice versa, but bug from version 2.4.3 ( http://code.opencv.org/issues/2616#note-1 ) prevents it from doing so. That explain why this code was compiling for original author few years ago, and not for me. Anyway, user @alrikai provided correct answer and workarround for this.

Error was corrected as: cv::circle(result, cv::Point2f(center), static_cast(radius), cv::Scalar(0), 2); so cv::Point(center) become this cv::Point2f(center)

Answer 1

As commented above, the problem was that you're making a cv::Point from a cv::Point2f. cv::Point is declared as typedef Point2i Point;, meaning that it's equivalent to a cv::Point2i. So in essence, you're trying to make a cv::Point2i from a cv::Point2f, which is invalid.

Also, glad to hear it worked for you