Is it configuration problem of opencv3.10 with qt 5.5? Showing Error "undefined reference to `cv::imread(cv::String const&, int)"

beginMyCoding

Hello I want to implement sobel operator, so for that i need to read matrix of the input image. I tried to perform with cv::imread() but i am getting the error

undefined reference to `cv::imread(cv::String const&, int)

this is my code below

mainwindow.cpp

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

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

    Mat src, dst;
    /// Load an image
    src = cv::imread("C:\\Users\\Prashanth KUMAR\\Pictures\\PhotoGrid_1448276690562.jpg");
      namedWindow("initial");
      imshow("initial", src);

          waitKey();
}

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

testSobel.pro

QT       += core gui

greaterThan(QT_MAJOR_VERSION, 4): QT += widgets

TARGET = TestSobel
TEMPLATE = app


SOURCES += main.cpp\
        mainwindow.cpp

HEADERS  += mainwindow.h

FORMS    += mainwindow.ui

I read in some posts that it is the problem of including opencv libraries in Qt.

But my Qt Build environment already has an opencv directory
here is the screenshot below
https://drive.google.com/file/d/0B6gtKf78_zVOLWFPWFFzRk5EeXc/view?usp=sharing

Or is there any other way to link opencv 3.10 with Qt Creator 5.5 in windows?

SGaist

Hi,

You need to tell your compiler that you want to link against the OpenCV libraries otherwise it won't know anything about them.

beginMyCoding

@SGaist Thanks for your reply.
I a new to Qt and OpenCV.
Can you explain in detail how to do that, or any link which explains that would be helpful?
I have searched a lot about this but nothing seems to work for me.

SGaist

What did you try ?
What error did you get ?
What compiler are you using ?

beginMyCoding

@SGaist I downloaded and extracted openCV. Later installed Qt. Added the directories
C:\Qt\5.5\mingw492_32\bin
C:\opencv\build\x86\vc12\bin
to the path in Environment variables.

Later downloaded CMake and installed it and added its path too.
Created an empty folder opencv-mingw

In CMake i selected
the sourcecode Directory as C:\Qt\Tools\mingw492_32\bin
Buid the binary in C:/opencv-mingw and hit configure button

Selected MinGW Makefiles from dropdown menu. Then it asked to specify native compilers
Specified C:/Qt/Tools/mingw491_32/bin/gcc.exe for C
specified C:/Qt/Tools/mingw491_32/bin/g++.exe for C++
and hit finish

IT GAVE ME ERROR
Error in configuration process, Project files may be invalid

SGaist

You are trying to link a Visual Studio build of OpenCV with a MinGW build of Qt. That won't work.

If already available in your package, use the MinGW version. Otherwise you have to compile OpenCV by hand.

beginMyCoding

@SGaist How to compile it manually?

SGaist

Take a look at the answer here