使用鼠标回调打印坐标和像素值

Question

这是我尝试的代码,只打印坐标值而不是像素值.

#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";

}

我得到的输出为: -

打印坐标值但不能正确打印像素值.我犯了什么错？

Answer 1

cout将uchar打印为字符,就像你看到的那样.

只需用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