Qt Creator - OpenCV - undefined reference/can't find libraries - c++

Question

Windows 7
Qt 5.4.0
OpenCV 2.4.10
Mingw 4.9.1
I'm trying to create a simple Hello World app, to test if Qt is working with OpenCV. Besides the stuff created by default, the code is
#include <opencv/cv.h>
#include <opencv/highgui.h>
(...)
cv::Mat image= cv::imread("pic.jpg");
cv::namedWindow("Test picture");
cv::imshow("Test picture", image);
cv::waitKey(1000);
(...)
However, I'm having trouble linking libraries. At first I've set the paths to *.dll.a files manually
INCLUDEPATH += C:/opencv/my_build/install/include
INCLUDEPATH += C:/opencv/my_build/install/include/opencv
INCLUDEPATH += C:/opencv/my_build/install/include/opencv2
LIBS += -LC:/opencv/my_build/install/x86/mingw/lib \
-llibopencv_core2410 \
-llibopencv_highgui2410
etc etc
But then I'd get a cannot find -llibopencv_<lib>2410 error. I've even used Qt Creator's "Add library" function (Projects -> rightclick -> add library), the result is the same. That error only goes away if I change -llibopencv_<lib>2410 to -opencv_<lib>2410. Which from my understanding is weird, as the "l" argument is missing.
Even though that error goes away, a bunch of others replace it, as I get undefined reference to cv::EVERYTHING error. I've looked around, found solutions to either problem, but solving one leads to the other and vice versa.
I'm fairly sure the OpenCV build is not at fault - I've already completed a pretty big console-ish app using it with Code::Blocks.
My current *.pro file :
QT += core gui
greaterThan(QT_MAJOR_VERSION, 4): QT += widgets
TARGET = OpenCVTest
TEMPLATE = app
SOURCES += main.cpp\
mainwindow.cpp
HEADERS += mainwindow.h
FORMS += mainwindow.ui
INCLUDEPATH += C:/opencv/my_build/install/include
win32: LIBS += -L$$PWD/../../../../../../OpenCV/my_build/install/x86/mingw/lib/ -llibopencv_core2410
INCLUDEPATH += $$PWD/../../../../../../OpenCV/my_build/install/x86/mingw
DEPENDPATH += $$PWD/../../../../../../OpenCV/my_build/install/x86/mingw
win32: LIBS += -L$$PWD/../../../../../../OpenCV/my_build/install/x86/mingw/lib/ -llibopencv_highgui2410
INCLUDEPATH += $$PWD/../../../../../../OpenCV/my_build/install/x86/mingw
DEPENDPATH += $$PWD/../../../../../../OpenCV/my_build/install/x86/mingw
How to correctly link the OpenCV libraries to Qt Creator? Am I missing something?
edit: I've rebuilt the whole damn thing and it still doesn't work. God damn it.

Answer 1

When specifying library, you need to exclude the 'lib' part:
LIBS += -LC:/opencv/my_build/install/x86/mingw/lib \
-lopencv_core2410 \
-lopencv_highgui2410

Answer 2

Frankly, I have little idea of what went wrong. I've edited the environment PATH variable, twice, to include the OpenCV build. Maybe I've made a typo the first time. It now looks like this:
C:\MinGW\bin;C:\OpenCV\my_build\install\x86\mingw\bin;C:\Qt\5.4.0\5.4\mingw491_32\bin;
My *.pro file also looks different.
QT += core
QT -= gui
greaterThan(QT_MAJOR_VERSION, 4): QT += widgets
TARGET = OpenCVTest
CONFIG += console
CONFIG -= app_bundle
TEMPLATE = app
INCLUDEPATH += C:/OpenCV/qtbuild//install/include
LIBS += "C:/OpenCV/qtbuild/install/x86\mingw/lib/*.a"
SOURCES += main.cpp\
mainwindow.cpp
HEADERS += mainwindow.h
FORMS += mainwindow.ui
I've change +=gui to -=gui and added CONFIG -= app_bundle. The INCLUDE and LIBS paths are also different now - I won't be changing them out of an irrational fear something will go horribly wrong again.
And lastly, I've simply removed the previous project and made a new one. Maybe something else got corrupted?
Anyway, it works now, after doing these things.