QT 调用 OpenCV 打开摄像头

发表于 更新于 分类于 阅读次数： 本文字数： 9.9k 阅读时长 ≈ 9 分钟

　　测试使用 MinGW-64 编译的OpenCV 是否正常，用 Qt 打开视频显示在 label。

当参见上文完成编译与安装后，你可以在 build/bin 下面看到各种动态库 ，本文的目的就是使用 Qt 来测试一下啊 OpenCV。


新建项目

打开Qt，新建一个Qt Widgets Application项目，添加1个label控件和2个pushButton按钮，修改pushButton按钮的名字为“开始”和“停止”，控件对象名改为 label_Video 、pushButton_Open 、 pushButton_Close

image-20200721173631890

image-20200721173739290

其它默认，勾选上 MinGW 64

image-20200721173821531

image-20200721174446565

接下来要添加“信号槽”，分别选中两个push button，右键选择**转到槽…**，然后选择clicked()，会自动创建信号与槽及其连接。当然也可以选择手动添加槽函数，并用 connect 连接。

image-20200721192645948


配置环境变量

为 E:\20200325\DevelopmentEnvironment\opencv3411\build\install\x64\mingw\bin 配置环境变量，记得重启一下。（ 我记得我以前配其它的不重启也行啊 ，但这个我的不重启不生效）

只要打开系统属性窗口并在“PATH”中添加一个新的对象元素就可以了。它们通常是用“;”隔开的，因此请在“;”后添加一个新项。注意，这个路径只与Windows操作系统相关，并且可以在这里找到OpenCV的DLL文件，以便使构建过程更加容易。Linux和macOS用户不需要对此做任何事情。


代码书写

参考 Qt5：opencv摄像头播放视频 或者 OpenCV 自带的例子。

其中 OpenCV 下的 例子的代码如下，是在 C++ MSVC 下的代码。参考其处理流程即可。

1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
#include <opencv2/core.hpp>
#include <opencv2/videoio.hpp>
#include <opencv2/highgui.hpp>
#include <opencv2/imgproc.hpp>  // cv::Canny()
#include <iostream>

using namespace cv;
using std::cout; using std::cerr; using std::endl;

int main(int, char**)
{
    Mat frame;
    cout << "Opening camera..." << endl;
    VideoCapture capture(0); // open the first camera
    if (!capture.isOpened())
    {
        cerr << "ERROR: Can't initialize camera capture" << endl;
        return 1;
    }

    cout << "Frame width: " << capture.get(CAP_PROP_FRAME_WIDTH) << endl;
    cout << "     height: " << capture.get(CAP_PROP_FRAME_HEIGHT) << endl;
    cout << "Capturing FPS: " << capture.get(CAP_PROP_FPS) << endl;

    cout << endl << "Press 'ESC' to quit, 'space' to toggle frame processing" << endl;
    cout << endl << "Start grabbing..." << endl;

    size_t nFrames = 0;
    bool enableProcessing = false;
    int64 t0 = cv::getTickCount();
    int64 processingTime = 0;
    for (;;)
    {
        capture >> frame; // read the next frame from camera
        if (frame.empty())
        {
            cerr << "ERROR: Can't grab camera frame." << endl;
            break;
        }
        nFrames++;
        if (nFrames % 10 == 0)
        {
            const int N = 10;
            int64 t1 = cv::getTickCount();
            cout << "Frames captured: " << cv::format("%5lld", (long long int)nFrames)
                 << "    Average FPS: " << cv::format("%9.1f", (double)getTickFrequency() * N / (t1 - t0))
                 << "    Average time per frame: " << cv::format("%9.2f ms", (double)(t1 - t0) * 1000.0f / (N * getTickFrequency()))
                 << "    Average processing time: " << cv::format("%9.2f ms", (double)(processingTime) * 1000.0f / (N * getTickFrequency()))
                 << std::endl;
            t0 = t1;
            processingTime = 0;
        }
        if (!enableProcessing)
        {
            imshow("Frame", frame);
        }
        else
        {
            int64 tp0 = cv::getTickCount();
            Mat processed;
            cv::Canny(frame, processed, 400, 1000, 5);
            processingTime += cv::getTickCount() - tp0;
            imshow("Frame", processed);
        }
        int key = waitKey(1);
        if (key == 27/*ESC*/)
            break;
        if (key == 32/*SPACE*/)
        {
            enableProcessing = !enableProcessing;
            cout << "Enable frame processing ('space' key): " << enableProcessing << endl;
        }
    }
    std::cout << "Number of captured frames: " << nFrames << endl;
    return nFrames > 0 ? 0 : 1;
}


我的 Qt 项目中完整的代码为：

QtOpenCVTest.pro

1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
QT       += core gui

greaterThan(QT_MAJOR_VERSION, 4): QT += widgets

CONFIG += c++11

# The following define makes your compiler emit warnings if you use
# any Qt feature that has been marked deprecated (the exact warnings
# depend on your compiler). Please consult the documentation of the
# deprecated API in order to know how to port your code away from it.
DEFINES += QT_DEPRECATED_WARNINGS

# You can also make your code fail to compile if it uses deprecated APIs.
# In order to do so, uncomment the following line.
# You can also select to disable deprecated APIs only up to a certain version of Qt.
#DEFINES += QT_DISABLE_DEPRECATED_BEFORE=0x060000    # disables all the APIs deprecated before Qt 6.0.0

SOURCES += \
    main.cpp \
    mainwindow.cpp

HEADERS += \
    mainwindow.h

FORMS += \
    mainwindow.ui

# Default rules for deployment.
qnx: target.path = /tmp/$${TARGET}/bin
else: unix:!android: target.path = /opt/$${TARGET}/bin
!isEmpty(target.path): INSTALLS += target

INCLUDEPATH += E:\20200325\DevelopmentEnvironment\opencv3411\build\install\include

LIBS += E:\20200325\DevelopmentEnvironment\opencv3411\build\install\x64\mingw\bin\libopencv_*.dll


注意，在上面的代码中，需要替换自己的路径。

mainwindow.h

1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
#ifndef MAINWINDOW_H
#define MAINWINDOW_H

#include <QMainWindow>
#include"opencv2/opencv.hpp"
#include "QTimer"
#include "QImage"

QT_BEGIN_NAMESPACE
namespace Ui { class MainWindow; }
QT_END_NAMESPACE
using namespace cv;
class MainWindow : public QMainWindow
{
    Q_OBJECT

public:
    MainWindow(QWidget *parent = nullptr);
    ~MainWindow();

private slots:
    void on_pushButton_Open_clicked();

    void on_pushButton_Close_clicked();

    void ReadCarmeraFrame();

private:
    Ui::MainWindow *ui;
    
    cv::VideoCapture capture;
    QTimer *timer;
    Mat frame;
};
#endif // MAINWINDOW_H

mainwindow.cpp

1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
#include "mainwindow.h"
#include "ui_mainwindow.h"
#include"QDebug"
MainWindow::MainWindow(QWidget *parent)
    : QMainWindow(parent)
    , ui(new Ui::MainWindow)
{
    ui->setupUi(this);
    
    setWindowTitle(" 测试 OpenCV 打开 摄像头");
    timer=new QTimer(this);
    connect(timer,&QTimer::timeout,this,& MainWindow::ReadCarmeraFrame);
    connect(ui->pushButton_Open, &QPushButton::clicked , this, &MainWindow::on_pushButton_Open_clicked  );//打开摄像头
    connect(ui->pushButton_Close, &QPushButton::clicked, this, &MainWindow::on_pushButton_Close_clicked);// 关闭摄像头
}

MainWindow::~MainWindow()
{
    delete ui;
}
void MainWindow::ReadCarmeraFrame()
{
    //获取图像帧
    capture>>frame;
    
    //将视频显示到label上
    QImage image = QImage((const uchar*)frame.data,frame.cols,frame.rows,QImage::Format_RGB888).rgbSwapped();
    ui->label_Video->setPixmap(QPixmap::fromImage(image));
    
    
}

//打开摄像头
void MainWindow::on_pushButton_Open_clicked()
{
    capture.open(0);//打开摄像头
    if (!capture.isOpened())
    {
        qDebug() << "ERROR: Can't initialize camera capture" << endl;
        // break;
    }
    
    qDebug() << "Frame width: " << capture.get(CAP_PROP_FRAME_WIDTH) << endl;
    qDebug() << "     height: " << capture.get(CAP_PROP_FRAME_HEIGHT) << endl;
    qDebug() << "Capturing FPS: " << capture.get(CAP_PROP_FPS) << endl;
    
    
    timer->start(25);//开启定时器，一次25ms
}

//关闭摄像头
void MainWindow::on_pushButton_Close_clicked()
{
    timer->stop();    //关闭定时器
    capture.release();//释放图像
}

mainwindow.ui 的 xml 为：

1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
<?xml version="1.0" encoding="UTF-8"?>
<ui version="4.0">
 <class>MainWindow</class>
 <widget class="QMainWindow" name="MainWindow">
  <property name="geometry">
   <rect>
    <x>0</x>
    <y>0</y>
    <width>995</width>
    <height>709</height>
   </rect>
  </property>
  <property name="sizePolicy">
   <sizepolicy hsizetype="Expanding" vsizetype="Expanding">
    <horstretch>0</horstretch>
    <verstretch>0</verstretch>
   </sizepolicy>
  </property>
  <property name="minimumSize">
   <size>
    <width>800</width>
    <height>550</height>
   </size>
  </property>
  <property name="windowTitle">
   <string>MainWindow</string>
  </property>
  <widget class="QWidget" name="centralwidget">
   <layout class="QGridLayout" name="gridLayout">
    <item row="0" column="0">
     <layout class="QVBoxLayout" name="verticalLayout">
      <item>
       <widget class="QLabel" name="label_Video">
        <property name="sizePolicy">
         <sizepolicy hsizetype="Expanding" vsizetype="Expanding">
          <horstretch>0</horstretch>
          <verstretch>0</verstretch>
         </sizepolicy>
        </property>
        <property name="text">
         <string>TextLabel</string>
        </property>
       </widget>
      </item>
      <item>
       <layout class="QHBoxLayout" name="horizontalLayout">
        <item>
         <widget class="QPushButton" name="pushButton_Open">
          <property name="text">
           <string>打开</string>
          </property>
         </widget>
        </item>
        <item>
         <widget class="QPushButton" name="pushButton_Close">
          <property name="text">
           <string>关闭</string>
          </property>
         </widget>
        </item>
       </layout>
      </item>
     </layout>
    </item>
   </layout>
  </widget>
  <widget class="QMenuBar" name="menubar">
   <property name="geometry">
    <rect>
     <x>0</x>
     <y>0</y>
     <width>995</width>
     <height>26</height>
    </rect>
   </property>
  </widget>
  <widget class="QStatusBar" name="statusbar"/>
 </widget>
 <resources/>
 <connections/>
</ui>


运行


crashed 问题解决

ShareX_20200721_194414_1365_332_qtcreator

问题：用qt creator写程序，运行发生crashed，一般是在程序中使用了第三方库，运行时找不到dll，在qt creator中运行会直接crashed，不提示原因。

解决办法：直接运行生成的exe文件，会提示缺少xxxdll，此时，直接将缺少的dll放到exe所在文件夹中，再次运行，成功。也可以将dll添加到系统路径中。总之，让程序找到调用的第三方库，就不会creashed了。
————————————————
版权声明：本文为CSDN博主「LoveCherish1993」的原创文章，遵循CC 4.0 BY-SA版权协议，转载请附上原文出处链接及本声明。
原文链接：https://blog.csdn.net/Joker_mw/article/details/79351076

解决方法有两个：

  • 第一种方法 需要将

  • E:\20200325\DevelopmentEnvironment\opencv3411\build\install\x64\mingw\bin

的动态库 dll 文件拷贝到运行的 exe 目录中

  • 第二种就是为

    E:\20200325\DevelopmentEnvironment\opencv3411\build\install\x64\mingw\bin

    配置环境变量，记得重启一下。（ 我记得我以前配其它的不重启也行啊 ，但这个我的不重启不生效）。


参考文献

Qt5：opencv摄像头播放视频

cv::VideoCapture Class Reference