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QT 调用 OpenCV 打开摄像头

  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_VideopushButton_OpenpushButton_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

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。

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#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

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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

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#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

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#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:

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<?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

觉得文章对您有帮助请我喝冰可乐吧 😉