Problem with Integrating QT Creator and OPENCV

[RG84]

Hello everyone,
I will apologize in advance for asking this because I know this is a topic that's been discussed , but unfortunately for me none of the many topics I've searched have helped me.

I am trying to write a simple program using opencv in QT CREATOR(few lines of code involving basic opencv functions), but am receiving errors as such:
" error: undefined reference to `cvNamedWindow' "
here is the pro file

HEADERS     =     patientdata.h \
    recordingSoftwareGui.h \
    functions.h \
    filemanagement.h \
    patienttrial.h \
    addtrialdialog.h \
    asciiTable.h \
    Rectangle.h \
    Point.h
SOURCES	    =  main.cpp \
    patientdata.cpp \
    functions.cpp \
    recordingSoftwareGui.cpp \
    filemanagement.cpp \
    patienttrial.cpp \
    addtrialdialog.cpp
FORMS       =     recordingSoftwareGui.ui \
    addtrialdialog.ui
 
INCLUDEPATH+= D:\OPENCV240MIN2\install\include\
D:\OPENCV240MIN2\install\include\opencv   \
D:\OPENCV240MIN2\install\include\opencv2   \
D:\OPENCV240MIN2\install\include\opencv2\calib3d \
D:\OPENCV240MIN2\install\include\opencv2\contrib \
D:\OPENCV240MIN2\install\include\opencv2\core \
D:\OPENCV240MIN2\install\include\opencv2\features2d \
D:\OPENCV240MIN2\install\include\opencv2\flann \
D:\OPENCV240MIN2\install\include\opencv2\gpu \
D:\OPENCV240MIN2\install\include\opencv2\highgui \
D:\OPENCV240MIN2\install\include\opencv2\legacy \
D:\OPENCV240MIN2\install\include\opencv2\ml \
D:\OPENCV240MIN2\install\include\opencv2\nonfree \
D:\OPENCV240MIN2\install\include\opencv2\objdetect \
D:\OPENCV240MIN2\install\include\opencv2\photo  \
D:\OPENCV240MIN2\install\include\opencv2\stitching \
D:\OPENCV240MIN2\install\include\opencv2\ts  \
D:\OPENCV240MIN2\install\include\opencv2\video   \
D:\OPENCV240MIN2\install\include\opencv2\videostab
 
LIBS+=-L"D:\OPENCV240MIN2\install\lib"

HEADERS     =     patientdata.h \
    recordingSoftwareGui.h \
    functions.h \
    filemanagement.h \
    patienttrial.h \
    addtrialdialog.h \
    asciiTable.h \
    Rectangle.h \
    Point.h
SOURCES	    =  main.cpp \
    patientdata.cpp \
    functions.cpp \
    recordingSoftwareGui.cpp \
    filemanagement.cpp \
    patienttrial.cpp \
    addtrialdialog.cpp
FORMS       =     recordingSoftwareGui.ui \
    addtrialdialog.ui

INCLUDEPATH+= D:\OPENCV240MIN2\install\include\
D:\OPENCV240MIN2\install\include\opencv   \
D:\OPENCV240MIN2\install\include\opencv2   \
D:\OPENCV240MIN2\install\include\opencv2\calib3d \
D:\OPENCV240MIN2\install\include\opencv2\contrib \
D:\OPENCV240MIN2\install\include\opencv2\core \
D:\OPENCV240MIN2\install\include\opencv2\features2d \
D:\OPENCV240MIN2\install\include\opencv2\flann \
D:\OPENCV240MIN2\install\include\opencv2\gpu \
D:\OPENCV240MIN2\install\include\opencv2\highgui \
D:\OPENCV240MIN2\install\include\opencv2\legacy \
D:\OPENCV240MIN2\install\include\opencv2\ml \
D:\OPENCV240MIN2\install\include\opencv2\nonfree \
D:\OPENCV240MIN2\install\include\opencv2\objdetect \
D:\OPENCV240MIN2\install\include\opencv2\photo  \
D:\OPENCV240MIN2\install\include\opencv2\stitching \
D:\OPENCV240MIN2\install\include\opencv2\ts  \
D:\OPENCV240MIN2\install\include\opencv2\video   \
D:\OPENCV240MIN2\install\include\opencv2\videostab

LIBS+=-L"D:\OPENCV240MIN2\install\lib"

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I have tried 5-6 different versions of opencv- some of which compiled with mingw , some of which precompiled with MSVC.
I have made sure to compile opencv with the same gcc and g++ that QT uses.
Yet I still am not making any progress ; I am using QT version 4.8.0 if that makes any difference.
Any help would be appreciated , thank you.

[ChrisW67]

Use / in preference to \ in file paths in the PRO file (actually anywhere in Qt).

Line 20 should have a space before the continuation \ or it will run together with line 21

Line 40 should list the libraries that you wish the program to link against (-l options). You currently list none, only a search location (-L option)