c++ - 主函数跳过线程并且不加入以显示所需的输出

Question

ProcessFrames 函数获取图像的一个象限，并对其应用 Canny 过滤器。但是创建的线程不会给出 Canny 检测到的图像。相反，我在 imshow() 中获取图像的颜色象限。

void ProcessFrames(Mat &image)
{
    Mat test = image;
    Canny(test, image, 5, 60, 3);
}

void main()
{
    Mat frame;
    Mat top_left, top_right, bot_left, bot_right;
    String filename = "C:\\Users\\operator\\Downloads\\MODFAM1080I.mpg";
    VideoCapture capture(filename);
    if (!capture.isOpened())
        throw "Error when reading video file!!";
    while (1)
    {
        capture >> frame;
        if (frame.empty())
        break;
        top_left = frame(Range(0, frame.rows / 2 - 1), Range(0, frame.cols / 2 - 1));
        top_right = frame(Range(0, frame.rows / 2 - 1), Range(frame.cols / 2, frame.cols - 1));
        bot_left = frame(Range(frame.rows / 2, frame.rows - 1), Range(0, frame.cols / 2 - 1));
        bot_right = frame(Range(frame.rows / 2, frame.rows - 1), Range(frame.cols / 2, frame.cols - 1));
        //Cropping the image into four quadrants to process it separately. 
        thread t1(ProcessFrames,top_left); //invoking a thread and passing first quadrant.
        t1.join(); //joing the thread with the main function
        imshow("Canny", top_left); // still shows color image of the first quadrant. Canny not reflected.
        cvWaitKey(10);
    }
}

Answer 1

std::thread 构造函数复制所有内容。如果你想传递数据指针并且这个数据要在线程中改变，你必须用 std::ref() 包装它。