重载“Point_(cv::Point2f&)”的调用不明确

Question

我正在为 OpenCV2 和 C++ 编写一些示例代码，但我被卡住了。编译器（Win7 上的 MinGW，g++ 4.7.2）说 调用重载的“Point_(cv::Point2f&)”是模棱两可的，但我找不到确切的问题所在。这是错误：

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);

这里是代码：

#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;
}

我做错了什么？

编辑：我希望一些投反对票的人尝试解决这个问题。 这不是这种类型的唯一问题，但我的已经被否决了 3 次？

此外，这是来自加拿大教授 (http://www.laganiere.name/opencvCookbook/) 所写书籍的示例，他同时教授 OpenCV，我应该比他更擅长这方面吗？我应该为我问这个感到羞耻吗？我是 C++ 和 OpenCV 的新手？我是否应该在其他十个论坛上提问，然后，如果我在 Stackoverflow 上找不到答案，请在此处提问？

此外，我并不懒惰，我帮助这个人重写了他的代码（OpenCV: record footage in one window and Display the same video in 2nd window but with contours only）。我帮助了一个比我了解少的人。但是，在这种情况下，我只是不知道如何在这段代码中解决这个问题，但在 30 分钟内我得到了 3 票否决票？

更新：正如 OpenCV 社区向我指出的那样，实际上应该允许将 Point 转换为 Point2f，反之亦然，但是 2.4.3 版（http://code.opencv.org/issues/2616#note-1）中的错误阻止了它这样做。这就解释了为什么几年前这段代码是为原作者编译的，而不是为我编译的。 无论如何，用户@alrikai为此提供了正确的答案和解决方法。

错误被纠正为：cv::circle(result, cv::Point2f(center), static_cast(radius), cv::Scalar(0), 2);所以 cv::Point(center) 变成了这个 cv::Point2f(center)

Answer 1

如上所述，问题在于您正在从cv::Point2f 制作cv::Point。 cv::Point 被声明为typedef Point2i Point;，这意味着它等同于cv::Point2i。所以本质上，你是在尝试从 cv::Point2f 中创建一个 cv::Point2i，这是无效的。

另外，很高兴听到它对你有用