Qt + OpenCV使用std :: thread播放视频 [英] Qt + OpenCV play videos with std::thread
问题描述
这是我的GUI,
我在这里要做的是一起显示四个不同的视频.用户输入特定视频文件的路径,然后单击打开",应创建一个新线程来播放该视频.
What I want to do here is to display four different videos together. Users input the path to a specific video file and click open, a new thread should be created to play that video.
我有一个名为startThread()的插槽,以及一个在名为openCamera()的线程中调用的函数;
I have a slot named startThread(), and a funciton to be called in thread named openCamera();
在mainwindow.hpp中,它具有
In mainwindow.hpp, it has
public:
static void openCamera(const std::string& address, QLabel* label);
private slots:
void startThread();
在mainwindow.cpp中,它具有
In mainwindow.cpp, it has
void MainWindow::startThread() {
std::string address;
QLabel* label;
// Get the input from GUI and assign it to std::string address
// and find the label corresponding to clicked button.
// ...
std::thread t(openCamera, address, label);
}
void MainWindow::openCamera(std::string address, QLabel* label) {
cv::VideoCapture cap(address);
cv::Mat frame;
while (cap.isOpened()) {
cap >> frame;
// cv::imwrite("/Users/wking/Desktop/test.jpg", frame); // This function works!
label->setPixmap(QPixmap::fromImage(QImage(frame.data, frame.cols, frame.rows, frame.step, QImage::Format_RGB888).rgbSwapped()));
}
}
我想通过使用std :: thread来实现这一点.但是,它什么也没显示.单击带有正确输入的按钮后,该程序不会更新标签.我在这里想念什么吗?谢谢.
I'd like to implement this by using std::thread. However, it shows nothing. The program doesn't update label after I clicked the button with correct input. Did I miss anything here? Thanks.
推荐答案
只有主线程(GUI线程)可以更新UI.
我有一个类似的项目.我使用QThread和Worker类.
Worker类具有读取视频文件的插槽.如果完成读取帧,它将发出信号.
在MainWindow中,我创建了一些QThreads,将工作对象移到线程中.
将信号框连接到带有完成功能的Worker上,以在标签上显示cv :: Mat.
Only main thread (GUI thread) can updates UI.
I have a similar project. I use QThread and Worker class.
Worker class has a slot to read video file. It will emit a signal if finish reading a frame.
In MainWindow, I create some QThreads, move worker objects to threads.
Connect signal frameFinished of Worker with a funtion to display cv::Mat on a label.
class Worker : public QObject
{
Q_OBJECT
public:
Worker(QString path, int id);
~Worker();
public slots:
void readVideo(QString path = "");
signals:
// frame and index of label which frame will be displayed
void frameFinished(cv::Mat frame, int index);
void finished(int index);
private:
QString filepath;
int index;
};
这是worker.cpp
Here is worker.cpp
#include "worker.h"
#include <QDebug>
#include <QThread>
#include <QTime>
Worker::Worker(QString path, int id) : filepath(path), index(id)
{
}
Worker::~Worker()
{
}
void Worker::readVideo(QString path)
{
if (path.length() > 0)
filepath = path;
cv::VideoCapture cap(filepath.toStdString());
if (! cap.isOpened())
{
qDebug() << "Can't open video file " << filepath;
emit finished(index);
return;
}
cv::Mat frame;
while (true)
{
cap >> frame;
if (frame.empty())
{
frame = cv::Mat(cv::Size(720, 576), CV_8UC3, cv::Scalar(192, 0, 0));
emit frameFinished(frame, index);
break;
}
emit frameFinished(frame.clone(), index);
QThread::msleep(30);
}
emit finished(index);
}
mainwindow.h
mainwindow.h
#ifndef MAINWINDOW_H
#define MAINWINDOW_H
#include <QMainWindow>
#include <opencv2/opencv.hpp>
#include "worker.h"
#define MAX_NUM_CAM 8
namespace Ui {
class MainWindow;
}
class QThread;
class QLabel;
class MainWindow : public QMainWindow
{
Q_OBJECT
public:
explicit MainWindow(QWidget *parent = 0);
~MainWindow();
void init();
private slots:
void displayFrame(cv::Mat frame, int index);
private:
Ui::MainWindow *ui;
int numCams;
QLabel *labels[MAX_NUM_CAM];
QThread* threads[MAX_NUM_CAM];
Worker* workers[MAX_NUM_CAM];
};
#endif // MAINWINDOW_H
mainwindow.cpp
mainwindow.cpp
#include "mainwindow.h"
#include "ui_mainwindow.h"
#include <QDebug>
#include <QThread>
#include <QLabel>
#include <QGridLayout>
MainWindow::MainWindow(QWidget *parent) :
QMainWindow(parent),
ui(new Ui::MainWindow)
{
ui->setupUi(this);
qRegisterMetaType< cv::Mat >("cv::Mat");
qDebug() << "Main thread " << QThread::currentThreadId();
init();
}
MainWindow::~MainWindow()
{
delete ui;
}
void MainWindow::init()
{
QGridLayout *grid = new QGridLayout;
int numCols = 2;
numCams = 4;
int row = 0, col = 0;
for (int i = 0; i < numCams; i++)
{
labels[i] = new QLabel;
row = i / numCols;
col = i % numCols;
grid->addWidget(labels[i], row, col);
threads[i] = new QThread;
workers[i] = new Worker(QString("/home/shang/Videos/%1.mp4").arg(i+1), i);
workers[i]->moveToThread(threads[i]);
connect(workers[i], SIGNAL(frameFinished(cv::Mat, int)), this, SLOT(displayFrame(cv::Mat,int)));
connect(threads[i], SIGNAL(started()), workers[i], SLOT(readVideo()));
connect(workers[i], SIGNAL(finished(int)), threads[i], SLOT(quit()));
connect(workers[i], SIGNAL(finished(int)), workers[i], SLOT(deleteLater()));
connect(threads[i], SIGNAL(finished()), threads[i], SLOT(deleteLater()));
threads[i]->start();
}
this->centralWidget()->setLayout(grid);
}
void MainWindow::displayFrame(cv::Mat frame, int index)
{
QPixmap p = QPixmap::fromImage(QImage(frame.data, frame.cols, frame.rows, frame.step, QImage::Format_RGB888).rgbSwapped());
p = p.scaled(QSize(frame.cols/2, frame.rows/2));
labels[index]->setPixmap(p);
}
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