How to setup Qt and openCV on Windows

How to setup Qt and openCV on Windows

Introduction

This article shows how to install Qt, build OpenCV, and run a basic OpenCV example. This article assumes Windows 10 has just been installed.

This procedure requires close to 10GB of disk space:

Qt: 5.06GB
opencv: 522MB
opencv-Build: 3.95GB
downloads:152MB  

This article uses information from the following pages: http://docs.opencv.org/2.4/doc/tutorials/introduction/windows_install/windows_install.html?highlight=installation http://www.laganiere.name/opencvCookbook/chap1s1_2.shtml

Windows 10, Qt 5.9, OpenCV 3.2.0

This guide is actual for Qt 5.12.2 with MinGW 7.3.0 and OpenCV 4.0.1 too

Qt

Installation

Download the Qt installer from www.qt.io, then choose "Download now". This will then download qt-unified-windows-x86-2.0.5-online.exe. Execute the program, then choose the following settings:

 Welcome to the Qt online installer: next
 Qt Account - your unified login to everything Qt: skip
 Setup-Qt: next
 installation folder: D:\Qt
 select components: Qt-Qt5.9-MingGW 5.3.0 32 bit
 select components: Qt-Tools-MinGW 5.3.0
 License Agreement: agree and next
 start menu shortcuts: next
 ready to install: install

Testing

Run D:\Qt\Tools\QtCreator\bin\qtcreator.exe

 File-New file or project-Qt Widgets Application-choose
 enter a name and a location: next
 select all kits: next
 Class information: MainWindow (defaults): Next
 Project management: Finish

Now a new project is made. Start debugging by choosing

 Debug-Start Debugging-Start debugging (F5)

Now the Qt tab in the Windows taskbar should turn into a progress bar. After some time a new empty window should pop up. Stop debugging either by pressing the red cross in the top right of this new window, or choose

 Debug-Stop debugging  

Adjust Qt

When you need to add, remove or update a component of Qt, this can be done by running D:\Qt\MaintenanceTool.exe:

 maintain Qt: Qt Account: Skip
 Setup Qt: Add or remove components: Next
 Select components: 
 next :update 

Cmake

Download cmake from cmake.org. In this guide, 3.7.2 is used. Start cmake-3.7.2-win64-x64.msi, then choose the following settinge:

 Welcome to the CMake etup Wizzard: next
 End-User License Agreement: [X] Accept and next
 Install options: [X] Add CMake to the system PATH for all users, next
 Destination folder: C:\Program Files\CMake (default), next
 Ready to install CMake, Install

OpenCV

Getting OpenCV

Download openCV from sourceforge. In this guide, version 3.2.0 is used. Start opencv-3.2.0-vc14.exe and let it extract to d:\ . Now the folder d:\opencv is created.

Add minGW to the windows PATH variable

Open the control panel, 
System and Security, 
System, 
Advanced system settings,
Environment Variables,
System Variables,
Variable Name: Path
Variable value: ;D:\Qt\Tools\mingw530_32\bin

Compiling OpenCV

Start C:\Program Files\CMake\bin\cmake-gui.exe then choose the following settings:

 Where is the source code: D:\opencv\sources
 where to build the binaries: D:\opencv-build

Then click Configure, let cmake create the build directory, and choose the following settings:

 Specify the generator for this project: MinGW Makefiles
 Specify native compilers, next
 Compilers C: D:\Qt\Tools\mingw530_32\bin\gcc.exe
 Compilers C++: D:\Qt\Tools\mingw530_32\bin\g++.exe
 Finish

 Check the box [X]WITH_QT
 Check the box [X]WITH_OPENGL
 set Qt5_DIR to D:\Qt\5.9\mingw53_32\lib\cmake\Qt5

Uncheck the box []ENABLE_PRECOMPILED_HEADERS

Then click configure again.

 Set QT_MAKE_EXECUTABLE to D:\Qt\5.9\mingw53_32\bin\qmake.exe
 Set Qt5Concurrent_DIR to D:\Qt\5.9\mingw53_32\lib\cmake\Qt5Concurrent
 Set Qt5Core_DIR to D:\Qt\5.9\mingw53_32\lib\cmake\Qt5Core
 Set Qt5Gui_DIR to D:\Qt\5.9\mingw53_32\lib\cmake\Qt5Gui
 Set Qt5Test_DIR to D:\Qt\5.9\mingw53_32\lib\cmake\Qt5Test
 Set Qt5Widgets_DIR to D:\Qt\5.9\mingw53_32\lib\cmake\Qt5Widgets
 Set Qt5OpenGL_DIR to D:\Qt\5.9\mingw53_32\lib\cmake\Qt5OpenGL
 Set CMAKE_BUILD_TYPE to Release or RelWithDebInfo

Then click configure again Then click generate

Next open cmd, and type the following commands. To speed up the compile, the -j flag can be used to run multiple compile jobs simultaneously. On an 8 core CPU, you can set it to 8 or higher, so all cores are used. On a core i7-3770@3.4GHz with 8GB ram, the compile takes about 6 minutes.

 d:
 cd d:\
 cd opencv-build  
 mingw32-make -j 8
 mingw32-make install
 
 

If, in the file opencv/sources/modules/videoio/src/cap_dshow.cpp, you have the following error : 'sprintf_instead_use_StringCbPrintfA_or_StringCchPrintfA' was not declared in this scope ...

try this :put the following line: #define NO_DSHOW_STRSAFE, before the line : #include "DShow.h"

If you have the error: ‘nullptr’ was not declared in this scope..

try this: in cmake check the box ENABLE_CXX11

If, in the file modules\videoio\src\cap_msmf.cpp you have the error: using invalid field '{anonymous}::ComPtr<T>::p'..

try this: in cmake unchecking WITH_MSMF

Add OpenCV compiled libraries to the windows PATH variable

Open the control panel, 
System and Security, 
System, 
Advanced system settings,
Environment Variables,
System Variables,
Variable Name: Path
Variable value: ;D:\opencv-build\install\x86\mingw\bin
 

Compile and run the example

Run D:\Qt\Tools\QtCreator\bin\qtcreator.exe

 File-New file or project-Qt Widgets Application-choose
 enter a name and a location: next
 select all kits: next
 Class information: MainWindow (defaults): Next
 Project management: Finish

Now a new project is made.

modify the .pro file like this:

#-------------------------------------------------
#
# Project created by QtCreator 2017-03-05T12:30:06
#
#-------------------------------------------------

QT       += core gui

greaterThan(QT_MAJOR_VERSION, 4): QT += widgets

TARGET = opencvtest
TEMPLATE = app

# The following define makes your compiler emit warnings if you use
# any feature of Qt which as been marked as 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 you use 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

INCLUDEPATH += D:\opencv\build\include

LIBS += D:\opencv-build\bin\libopencv_core320.dll
LIBS += D:\opencv-build\bin\libopencv_highgui320.dll
LIBS += D:\opencv-build\bin\libopencv_imgcodecs320.dll
LIBS += D:\opencv-build\bin\libopencv_imgproc320.dll
LIBS += D:\opencv-build\bin\libopencv_features2d320.dll
LIBS += D:\opencv-build\bin\libopencv_calib3d320.dll

# more correct variant, how set includepath and libs for mingw
# add system variable: OPENCV_SDK_DIR=D:/opencv/opencv-build/install
# read http://doc.qt.io/qt-5/qmake-variable-reference.html#libs

#INCLUDEPATH += $$(OPENCV_SDK_DIR)/include

#LIBS += -L$$(OPENCV_SDK_DIR)/x86/mingw/lib \
#        -lopencv_core320        \
#        -lopencv_highgui320     \
#        -lopencv_imgcodecs320   \
#        -lopencv_imgproc320     \
#        -lopencv_features2d320  \
#        -lopencv_calib3d320

and modify mainwindow.cpp like this:

#include "mainwindow.h"
#include "ui_mainwindow.h"

#include <opencv2/core/core.hpp>
#include <opencv2/highgui/highgui.hpp>

MainWindow::MainWindow(QWidget *parent) :
    QMainWindow(parent),
    ui(new Ui::MainWindow)
{
    ui->setupUi(this);

    // read an image
    cv::Mat image = cv::imread("f://1.jpg", 1);
    // create image window named "My Image"
    cv::namedWindow("My Image");
    // show the image on window
    cv::imshow("My Image", image);
}

MainWindow::~MainWindow()
{
    delete ui;
}

Place an image with the name "1.img" in the root of F:\, then run the example. Now 2 windows should pop up. One with the image, and one with an empty window.