C/C++开发，opencv与qt结合播放视频-编程知识

一、qt_ui创建

1.1 ui设置

1.2 ui及代码输出保存

二、创建工程

2.1 工程目录及编译设置

2.2 源码设计

三、编译及测试

3.1 程序编译

3.2 程序运行

首先声明，这是一个OpenCV 3学习文档的案例，但是说明有些过于省略，只有一些简短的代码描述，本人在学习验证过程中将其记录下来分享给大家。

一、qt_ui创建

1.1 ui设置

本文采用qt5.8_msvc2015_64版本，

进入qt的bin目录，打开qt_ui设计工具designer.exe

创建一个Widget窗体，即对象QWidget，命名为QMoviePlayer。

随后创建一个QFrame对象，对象名为frame，该对象可以随意在窗体QMoviePlayer拉出一个合适的长宽比显示框，该显示框用来显示视频使用。

完成设置后，保存该UI，例如QMoviePlayer.ui

1.2 ui及代码输出保存

本人的QMoviePlayer.ui文件的xml内容如下：

<?xml version="1.0" encoding="UTF-8"?>
<ui version="4.0"><class>QMoviePlayer</class><widget class="QWidget" name="QMoviePlayer"><property name="geometry"><rect><x>0</x><y>0</y><width>600</width><height>303</height></rect></property><property name="windowTitle"><string>Form</string></property><widget class="QFrame" name="frame"><property name="geometry"><rect><x>0</x><y>0</y><width>601</width><height>241</height></rect></property><property name="frameShape"><enum>QFrame::StyledPanel</enum></property><property name="frameShadow"><enum>QFrame::Raised</enum></property></widget></widget><resources/><connections/>
</ui>

点击窗体菜单，进入查看代码，保存该代码文件为ui_QMoviePlayer.h，或新创建一个头文件将该内容直接复制到头文件中保存。

本人的ui_QMoviePlayer.h的代码内容如下。

/********************************************************************************
** Form generated from reading UI file 'QMoviePlayerp15136.ui'
**
** Created by: Qt User Interface Compiler version 5.8.0
**
** WARNING! All changes made in this file will be lost when recompiling UI file!
********************************************************************************/#ifndef QMOVIEPLAYERP15136_H
#define QMOVIEPLAYERP15136_H#include <QtCore/QVariant>
#include <QtWidgets/QAction>
#include <QtWidgets/QApplication>
#include <QtWidgets/QButtonGroup>
#include <QtWidgets/QFrame>
#include <QtWidgets/QHeaderView>
#include <QtWidgets/QWidget>QT_BEGIN_NAMESPACEclass Ui_QMoviePlayer
{
public:QFrame *frame;void setupUi(QWidget *QMoviePlayer){if (QMoviePlayer->objectName().isEmpty())QMoviePlayer->setObjectName(QStringLiteral("QMoviePlayer"));QMoviePlayer->resize(600, 303);frame = new QFrame(QMoviePlayer);frame->setObjectName(QStringLiteral("frame"));frame->setGeometry(QRect(0, 0, 601, 241));frame->setFrameShape(QFrame::StyledPanel);frame->setFrameShadow(QFrame::Raised);retranslateUi(QMoviePlayer);QMetaObject::connectSlotsByName(QMoviePlayer);} // setupUivoid retranslateUi(QWidget *QMoviePlayer){QMoviePlayer->setWindowTitle(QApplication::translate("QMoviePlayer", "Form", Q_NULLPTR));} // retranslateUi};namespace Ui {class QMoviePlayer: public Ui_QMoviePlayer {};
} // namespace UiQT_END_NAMESPACE#endif // QMOVIEPLAYERP15136_H

二、创建工程

2.1 工程目录及编译设置

创建一个opencv_qt目录的工程文件，工程组织如下：

opencv_qtbinbuild_vcsrcmain.cppui_QMoviePlayer.hQMoviePlayer.hQMoviePlayer.cppQMoviePlayer.uiCMakeLists.txt      #cmake工程vcbuild_2015.bat    #编译命令

ui_QMoviePlayer.h和QMoviePlayer.ui就是前面采用designer.exe实现的ui及代码头文件。

CMakeLists.txt文件内容如下，本文给出的有win/linux的痕迹，但是本文只实现了基于vc2015+qt_vc2015+opencv_vc的win编译方式，Linux下本文并没有进行测试，有兴趣的读者可以按该模块调整支持实现（关于opencv的Linux下库编译及调用案例看本专栏其他博文）。qt链接采用了动态库，opencv的基于vc2015编译出来的库本文时预先编译好的（C/C++开发，opencv在win下安装及应用_c++安装opencv库_py_free-物联智能的博客-CSDN博客）。

# CMake 最低版本号要求
cmake_minimum_required (VERSION 3.1.0)
# 项目信息
set(proname "opencv_qt")
project(${proname} VERSION 1.0.0 LANGUAGES CXX)if(WIN32)message(STATUS "windows compiling...")set(CMAKE_CXX_FLAGS_RELEASE "${CMAKE_CXX_FLAGS_RELEASE} /MT")set(CMAKE_CXX_FLAGS_DEBUG "${CMAKE_CXX_FLAGS_DEBUG} /MTd")add_compile_options("$<$<C_COMPILER_ID:MSVC>:/utf-8>")add_compile_options("$<$<CXX_COMPILER_ID:MSVC>:/utf-8>")add_definitions(-D_PLATFORM_IS_WINDOWS_-D_CRT_SECURE_NO_WARNINGS-D_WINSOCK_DEPRECATED_NO_WARNINGS# -DZLIB_WINAPI-DUNICODE-D_UNICODE# -DQT_DLL# -DQT_CORE_LIB# -DQT_GUI_LIB# -DQT_WIDGETS_LIB# -D CMAKE_CXX_FLAGS="/utf-8")else(WIN32)message(STATUS "linux compiling...")# set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -std=c++11 -I/usr/include -L/lib/x86_64-linux-gnu -lpthread -pthread -lm -lrt -ldl -lz -luuid ")  #qt需要-fPIC编译指定add_definitions(-D_PLATFORM_IS_LINUX_"-g"# "-std=gnu++0x""-std=c++11""-O2"# "-pipe""-Wno-invalid-source-encoding""-Wdeprecated-declarations""-W""-fPIC""-Wall"# "-Werror"# "-Wshadow"# "-Wformat"# "-Wpointer-arith""-D_REENTRANT"# "-D_USE_FAST_MACRO"# "-Wno-long-long"# "-Wuninitialized"# "-D_POSIX_PTHREAD_SEMANTICS"# "-Wno-unused-parameter""-fexceptions""-DQT_NO_DEBUG""-DDQT_QML_DEBUG")
endif(WIN32)set(CMAKE_CXX_STANDARD 11)
set(CMAKE_CXX_STANDARD_REQUIRED ON)if(CMAKE_VERSION VERSION_LESS "3.7.0")set(CMAKE_INCLUDE_CURRENT_DIR ON)
endif()set(EXECUTABLE_OUTPUT_PATH   ${PROJECT_SOURCE_DIR}/bin)
# 创建 EXECUTABLE_OUTPUT_PATH 指向的文件夹
execute_process( COMMAND ${CMAKE_COMMAND} -E make_directory ${EXECUTABLE_OUTPUT_PATH})set(PROJECT_CUR_DIR .)if(WIN32)
set(QTDIR "D:/workForSoftware/Qt/Qt5.8.0/5.8/msvc2015_64")
else(WIN32)
set(QTDIR "/opt/qt-5.8_static")
endif(WIN32)
message("QTDIR = ${QTDIR}")
set(Qt5_DIR "${QTDIR}/lib/cmake/Qt5")
message("Qt5_DIR  = ${Qt5_DIR}")set(CMAKE_AUTOMOC ON)
# set(CMAKE_AUTORCC ON)
set(CMAKE_AUTOUIC ON)
#查找需要的Qt库文件，最好每一个库都要写，Qt也会根据依赖关系自动添加
find_package(Qt5 COMPONENTS Core Gui Widgets REQUIRED)
cmake_policy(SET CMP0020 NEW)set(CMAKE_INCLUDE_CURRENT_DIR ON) #包含编译目录FILE(GLOB srcfile ${PROJECT_CUR_DIR}/src/*.h ${PROJECT_CUR_DIR}/src/*.cpp )             #加载文件夹下的所有源码文件
LIST(APPEND code_file ${srcfile} ) #变量合并include_directories("${PROJECT_CUR_DIR}""${PROJECT_CUR_DIR}/src""${PROJECT_CUR_DIR}/../../opencv_vc/include""${QTDIR}/include""${QTDIR}/include/QtCore""${QTDIR}/include/QtGui""${QTDIR}/include/QtWidgets"
)#link 目录
link_directories("${QTDIR}/lib""${PROJECT_CUR_DIR}/../../opencv_VC/x64/vc14/lib"
)message("RESOURCES = ${RESOURCES}")add_executable(${proname}  ${code_file} ${RESOURCES} ${RC_FILE} )# 链接指定
set(link_lib Qt5::Core Qt5::Gui Qt5::Widgets
)
if(WIN32)
if (CMAKE_BUILD_TYPE STREQUAL "release")
set(link_lib_opencv opencv_img_hash460.lib opencv_world460.lib
)
else()
set(link_lib_opencv opencv_img_hash460d.lib opencv_world460d.lib
)
endif()
endif(WIN32)target_link_libraries(${proname} ${link_lib}${link_lib_opencv}
)#去除 CMD 窗口
if(WIN32)
message("CMAKE_BUILD_TYPE =${CMAKE_BUILD_TYPE}")
if (CMAKE_BUILD_TYPE STREQUAL "release")
if(MSVC)set_target_properties(${proname} PROPERTIESWIN32_EXECUTABLE YESLINK_FLAGS "/ENTRY:mainCRTStartup")
elseif(CMAKE_COMPILER_IS_GNUCXX)SET(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -mwindows") # Not tested
else()message(SEND_ERROR "You are using an unsupported Windows compiler! (Not MSVC or GCC)")
endif(MSVC)
endif()endif(WIN32)

vcbuild_2015.bat是为了编译方便创建的一个脚本，读者也可以按该脚本命令手动编译。

md build_vc
cd ./build_vc
@REM 单独编译时可能需要独立设置环境变量
if [%vccompilerversion%] EQU  [] ( set vccompilerversion="Visual Studio 14 2015 Win64" )@REM 工程配置
cmake -G %vccompilerversion% .. -DCMAKE_BUILD_TYPE=debug
@REM 编译
cmake --build . --config debug@REM 工程配置
cmake -G %vccompilerversion% .. -DCMAKE_BUILD_TYPE=release
@REM 编译
cmake --build . --config releasecd ..

2.2 源码设计

下来看看源码如何实现视频读取与播放的。

QMoviePlayer.h内容如下，该头文件定义了一个窗口类型，该窗口显示部分来自于前面的UI设计“Ui::QMoviePlayer ui”，定义了“cv::VideoCapture m_cap”用来捕获视频内容：

#ifndef _QMOVIEPLAYER_H_
#define _QMOVIEPLAYER_H_#include "ui_QMoviePlayer.h"
#include <QtWidgets/QWidget>
#include <QImage>#include <opencv2/opencv.hpp>
#include <string>
using namespace std;QT_BEGIN_NAMESPACE
class QPaintEvent;
class QTimer;
QT_END_NAMESPACEclass QMoviePlayer : public QWidget 
{Q_OBJECTpublic:QMoviePlayer(QWidget *parent = NULL);virtual ~QMoviePlayer(){;}bool open( string file );public slots:void nextFrame();private:void paintEvent( QPaintEvent* q);void _copyImage( void);private:Ui::QMoviePlayer ui;    //ui界面cv::VideoCapture m_cap; //opencv的视频读取及捕获图像实现QImage m_qt_img;cv::Mat m_cv_img;       //图像缓存矩阵QTimer* m_timer;
};#endif //_QMOVIEPLAYER_H_

QMoviePlayer.cpp内容如下，open函数用于打开一个视频文件，并通过QTimer对象来定期读取帧图像数据，nextFrame用于读取图像数据并更新到窗口显示；_copyImage函数是opencv与QT结合的关键，它将opencv捕获的图像m_cv_img转换为qt的图像m_qt_img，这样才能将图片按qt方式刷新到窗口显示：

#include "QMoviePlayer.h"#include <QPainter>
#include <QTimer>QMoviePlayer::QMoviePlayer(QWidget *parent): QWidget(parent)
{ui.setupUi( this );
}bool QMoviePlayer::open( string file)
{if( !m_cap.open( file)) return false;// If we opened the file, set up everything now://m_cap.read( m_cv_img );m_qt_img = QImage(QSize( m_cv_img.cols,m_cv_img.rows),QImage::Format_RGB888);ui.frame->setMinimumSize( m_qt_img.width(),m_qt_img.height());ui.frame->setMaximumSize( m_qt_img.width(),m_qt_img.height());_copyImage();m_timer = new QTimer( this );connect(m_timer, SIGNAL( timeout()), this, SLOT( nextFrame()) );m_timer->start( 1000.0 / m_cap.get( cv::CAP_PROP_FPS));return true;
}void QMoviePlayer::nextFrame()
{// Nothing to do if capture object is not open//if( !m_cap.isOpened()) return;m_cap.read(m_cv_img);if(m_cv_img.empty()) return;_copyImage();this->update();
}void QMoviePlayer::paintEvent( QPaintEvent* e )
{QPainter painter( this );painter.drawImage( QPoint( ui.frame->x(),ui.frame->y()),m_qt_img);
}void QMoviePlayer::_copyImage( void)
{// Copy the image data into the Qt QImage//cv::Mat cv_header_to_qt_image(cv::Size(m_qt_img.width(),m_qt_img.height()),CV_8UC3,m_qt_img.bits());cv::cvtColor(m_cv_img,cv_header_to_qt_image, cv::COLOR_BGR2RGB);
}

main.cpp文件内容如下，就是qt程序启动后，调用前面定义的QMoviePlayer对象，读取视频文件（argv[1]）及刷新显示：

#include <QApplication>
#include <QMoviePlayer.h>int main( int argc, char* argv[])
{QApplication app( argc, argv);QMoviePlayer mp;mp.open( argv[1]);mp.show();return app.exec();
}