c++ - 在简单的 C++ OpenCV 项目中使用 pthread

Question

我正在尝试在我的 OpenCV 项目中使用 pthread。最初我只是尝试使用两个不同的线程打开两个不同的图像。在Windows7 + VS2010 + pthreads-win32 lib上，程序运行良好。

但在我的 Debian jessei 机器(Opencv 2.4.1)上，相同的代码虽然编译得很好，但它的执行崩溃并出现以下错误。

[xcb] Unknown request in queue while dequeuing
[xcb] Most likely this is a multi-threaded client and XInitThreads has not been called
[xcb] Aborting, sorry about that.
pthreadTest: ../../src/xcb_io.c:179: dequeue_pending_request: Assertion `!xcb_xlib_unknown_req_in_deq' failed.
Aborted

有趣的是，当只创建 1 个线程时 [for (i=0; i<1; i++)]，它运行良好，并显示图像。

我已经花了 1.5 天的时间试图解决它，但没有成功。有谁知道，我做错了什么？

代码如下:

#include "opencv2/imgproc/imgproc.hpp"
#include "opencv2/highgui/highgui.hpp"
#include <cstdio>
#include <iostream>
#include <pthread.h>

using namespace cv;
using namespace std;

struct thread_data {
    bool isBig;
    string fileName;
};


void *processImg(void *args)
{
    struct thread_data *data = (struct thread_data *) args;
    const char * inputImgWinName = data->isBig ? "Big Img" : "Small Img";

    cv::Mat imgInput = imread(data->fileName, 1);

    cv::namedWindow(inputImgWinName, cv::WINDOW_AUTOSIZE);
    cv::imshow(inputImgWinName, imgInput);

    cv::waitKey();
    pthread_exit(NULL);
    //return NULL;
}


int main( int argc, char** argv )
{
    struct thread_data data[2];

    data[0].isBig = true;
    data[0].fileName = "img1.png";

    data[1].isBig = false;
    data[1].fileName = "img2.png";

    pthread_t threads[2];
    pthread_attr_t attr;
    void *status;

    // Initialize and set thread joinable
    pthread_attr_init(&attr);
    pthread_attr_setdetachstate(&attr, PTHREAD_CREATE_JOINABLE);

    // Create Threads 
    int rc;
    for (int i=0; i<2; i++) {
        rc = pthread_create(&threads[i], &attr, processImg, (void *)&(data[i]));
        if (rc) {
            cout << "Error: Unable to create thread";
            return -1;
        }
    }

    // free attribute and wait for the other threads
    pthread_attr_destroy(&attr);
    for (int i=0; i<2; i++) {
        rc = pthread_join(threads[i], &status);
        if (rc){
            cout << "Error:unable to join," << rc << endl;
            exit(-1);
        }
        cout << "Thread: "<< i <<" exiting with status: " << status << endl;
    }

    pthread_exit(NULL);
        return 0;
}

PS:由于某些原因，我无法使用 C++11 thread.h。

Answer 1

namedWindow，waitKey 应该离开你的线程，你在这里干扰桌面/gui