使用鼠标回调打印坐标和像素值

Question

这是我尝试的代码，仅打印坐标值，但不打印像素值。

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

void onMouse( int event, int x, int y, int, void* );
using namespace cv;

Mat img = cv::imread("b.jpg", 0); // force grayscale
Mat thresh=Mat::zeros(img.size(),CV_8UC1);

int main(int argc, char **argv)
{

    if(!img.data) {
        std::cout << "File not found" << std::endl;
        return -1;
    }

   threshold(img,binary,50,255,THRESH_TOZERO);  

   namedWindow("thresh");
   setMouseCallback( "thresh", onMouse, 0 );

   imshow("thresh",thresh);
}

void onMouse( int event, int x, int y, int, void* )
{
    if( event != CV_EVENT_LBUTTONDOWN )
            return;

    Point pt = Point(x,y);
    std::cout<<"x="<<pt.x<<"\t y="<<pt.y<<"\t value="<<thresh.at<uchar>(x,y)<<"\n";

}

我的输出为： -

打印坐标值但未正确打印像素值。我犯了什么错误？

Answer 1

cout打印char作为字符，就像你看到的那样。

将它们用cast转换为int进行打印：

cout << int( thresh.at<uchar>(y,x) )

also note, that it's at<uchar>(y,x), not x,y