c ++ - ne peut pas saisir la trame dans OpenCV - Stack Overflow

I have been trying to get openCV to read an image from my computer's webcam. The code below successfully opens the webcam (green light turns on). However, attempts to grab a frame and hence read a frame fail. I am at a loss here. Can anyone help?

Many Thanks, Hillary

P.S. I am running Mac OS X 10.9 on a MacBook Pro. And my opencv version is 2.4.6.1

And here is the code:

#include "opencv.hpp"
using namespace cv;

int main(int, char**) {

    VideoCapture cap = VideoCapture(0); 

    if(!cap.isOpened()){
       printf("failed to open camera\n");
       return -1;
    }

    namedWindow("edges",1);

    for(;;){
        if(waitKey(50) >= 0 ) break;

        if(!cap.grab()){
            printf("failed to grab from camera\n");
        }
    } 

    return 0;
}

You forgot to read new frames in your loop and show them! There:

for(;;){
    if(waitKey(50) >= 0 ) break;
    Mat frame;
    if(!cap.grab()){
        printf("failed to grab from camera\n");
        break;
    }
    cap >> frame; 

    if(frame.empty()){
        printf("failed to grab from camera\n");
        break;
    }

    imshow("edges", frame);
} 

I have been trying to get openCV to read an image from my computer's webcam. The code below successfully opens the webcam (green light turns on). However, attempts to grab a frame and hence read a frame fail. I am at a loss here. Can anyone help?

Many Thanks, Hillary

P.S. I am running Mac OS X 10.9 on a MacBook Pro. And my opencv version is 2.4.6.1

And here is the code:

#include "opencv.hpp"
using namespace cv;

int main(int, char**) {

    VideoCapture cap = VideoCapture(0); 

    if(!cap.isOpened()){
       printf("failed to open camera\n");
       return -1;
    }

    namedWindow("edges",1);

    for(;;){
        if(waitKey(50) >= 0 ) break;

        if(!cap.grab()){
            printf("failed to grab from camera\n");
        }
    } 

    return 0;
}

You forgot to read new frames in your loop and show them! There:

for(;;){
    if(waitKey(50) >= 0 ) break;
    Mat frame;
    if(!cap.grab()){
        printf("failed to grab from camera\n");
        break;
    }
    cap >> frame; 

    if(frame.empty()){
        printf("failed to grab from camera\n");
        break;
    }

    imshow("edges", frame);
} 

Source