How to link opencv in QtCreator and use Qt library - c++

Question

This question must be duplicate many times, but it just doesn't work and sometimes it still remains unanswered. Sources of information are mainly these
http://www.laganiere.name/opencvCookbook/chap1s1_2.shtml
http://www.youtube.com/watch?v=dgcXYQijV6c
This is the summation of what I think one should/can do. (And now it works for me.) Hopefully I mentioned everything from the very beginning, the aim is to write a very clear tutorial.
Installation of OpenCV for QtCreator
I have already MS Visual Studio 2010 Professional installed. (I have a free licence as a student) - I think this is not necessary, just a mention
Download: Qt 5.0.1 for Windows 32-bit (MinGW 4.7, 823 MB)
2.1 Install: Warning, everything that Qt uses (e.g. OpenCV) must be in directories that don't contain white-spaces in their names. - i.e. "Program Files" is wrong. (But I don't want different program files to accumulate directly on C, so I've only made a folder "Programs" in which everything important is installed)
Download: cmake-2.8.10.2-win32-x86.exe - Install for all users (this can be in Program Files)
Download: OpenCV-2.4.0.exe, extract to: C:\Programs\opencv24 - it'll create a dir "opencv"; add another folder "opencv_bin". Now it looks like this:
C:\Programs\opencv24\opencv*
C:\Programs\opencv24\opencv_bin
Set PATH environment variable, so that there be a link to MinGW compiler. e.g. C:\Programs\Qt\Qt5.0.1\Tools\MinGW\bin;
Start cmake-gui.exe
6.1 source code: set the default dir for OpenCV; C:\Programs\opencv24\opencv
6.2 binaries: set the opencv_bin dir; C:\Programs\copencv24\opencv_bin
6.3 click configure:
Choose MinGW Makefiles and Specify native compilers, click next
Field C is for gcc.exe; C:/Programs/Qt/Qt5.0.1/Tools/MinGW/bin/gcc.exe
Field C++ is for g++.exe; C:/Programs/Qt/Qt5.0.1/Tools/MinGW/bin/g++.exe
Field fortran can be empty, click finish
6.4 Many red lines will appear To the search field enter one by one: WITH_QT, WITH_TBB, WITH_IPP, WITH_CUDA, CMAKE_BUILD_TYPE
WITH_QT - must be selected.
WITH_TBB, WITH_IPP, WITH_CUDA - must be unselected
CMAKE_BUILD_TYPE - click and enter a text "Debug" (without quotes).
Clear the text from the Search field.
6.5 click configure and keep clicking configure until all red lines are gone, then click generate and close cmake-gui.exe
Go to the terminal (~command prompt), cd to the directory where are the builds (opencv_bin) and type mingw32-make
When the process ends after a long time, type mingw32-make install
Add into Path variable the path to the QtCreator/bin C:\Programs\Qt\Qt5.0.1\Tools\QtCreator\bin
Now I have created a new console app in QtCreator.
//cvHello.pro
QT += core
QT -= gui
TARGET = cvHello
CONFIG += console
CONFIG -= app_bundle
TEMPLATE = app
INCLUDEPATH += C:/Programs/opencv24/opencv_bin2/install/include
LIBS += "C:/Programs/opencv24/opencv_bin2/bin/*.dll"
SOURCES += main.cpp
OTHER_FILES += \
img.JPG
And the main file:
//main.cpp
#include <iostream>
#include "opencv2/core/core.hpp"
#include "opencv2/highgui/highgui.hpp"
#include "opencv/cv.h"
using namespace std;
int main()
{
cout << "Hello World!" << endl;
cv::Mat mat;
mat = cv::imread("img.JPG");
cvNamedWindow("hello");
cv::imshow("hello",mat);
cvWaitKey(0);
return 0;
}

Answer 1

Finally I am starting to be happy. When adjusting this question I had to try all the ways how to define LIBS. Listing them manually helped, at first I wrote them somehow wrong.
This is how it works finally:
LIBS += -LC:\\Programs\\opencv24\\opencv_bin2\\bin \
libopencv_core240d \
libopencv_highgui240d \
libopencv_imgproc240d \
libopencv_features2d240d \
libopencv_calib3d240d \

Answer 2

The originally accepted answer did not work for me, I am running MSVC2013 Professional and QT5.9. I found SIMPLE and SUREFIRE CROSS-PLATFORM solution that should help anyone who is trying to link an external library (like openCV) with QT.
The steps listed below are found in the Qt5 documentation: http://doc.qt.io/qtcreator/creator-project-qmake-libraries.html under the "To Add Library" section.
Right click on the project file located in the 'project pane' on the left side of the creator... and select "Add Library..."
Follow the instructions of the wizard
Let me add some specificity from here:
Select "External Library"
For the "Library File" navigate to your opencv_worldXXX.lib file (or opencv_worldXXXd.lib file, you will notice that by specifying only one or the other the wizard has a checkbox which includes the other automatically) [ex. ...\opencv\build\x64\vc12\lib\opncv_world310.lib]
For the "Include Folder" navigate to the "include" folder within the build. [ex. ...\opencv\build\include]
Select your operating system, dynamic/static library (whichever is appropriate)
Hit NEXT, CLEAN UP, and RUN!