OpenCV Functions not Found by Linker - c++

Question

The compiler can find all the required OpenCV header files, but it cannot find the functions included in the OpenCV library.
cv::CascadeClassifier::~CascadeClassifier()'
/usr/bin/ld: ComputerVision.cpp:(.text+0x688): undefined reference to cv::Mat::deallocate()'
/usr/bin/ld: ComputerVision.cpp:(.text+0x694): undefined reference to cv::Mat::deallocate()'
/usr/bin/ld: ComputerVision.cpp:(.text+0x6a0): undefined reference to cv::Mat::deallocate()'
/usr/bin/ld: ComputerVision.cpp:(.text+0x6ac): undefined reference to cv::Mat::deallocate()'
/usr/bin/ld: ComputerVision.cpp:(.text+0x6dc): undefined reference to cv::VideoCapture::~VideoCapture()'
/usr/bin/ld: ComputerVision.cpp:(.text+0x6e4): undefined reference to cv::CascadeClassifier::~CascadeClassifier()'
/usr/bin/ld: ComputerVision.o: in function cv::Mat::~Mat()':
ComputerVision.cpp:(.text._ZN2cv3MatD2Ev[_ZN2cv3MatD5Ev]+0x90): undefined reference to cv::fastFree(void)'
/usr/bin/ld: ComputerVision.cpp:(.text._ZN2cv3MatD2Ev[_ZN2cv3MatD5Ev]+0x9c): undefined reference to `cv::Mat::deallocate()'
collect2: error: ld returned 1 exit status
make: ** [Makefile:158: DoorLock] Error 1
/usr/bin/ld: cannot find -lopencv_core
/usr/bin/ld: cannot find -lopencv_imgproc
/usr/bin/ld: cannot find -lopencv_highgui
Update - I copied all the required OpenCV libraries into my usr/lib directory, and that seemed to work. But now I am getting the following error:
libopencv_videoio.so.4.1: error adding symbols: DSO missing from command line
For reference, he is my qmake (.pro) file:
######################################################################
# Automatically generated by qmake (3.1) Sat Nov 27 20:12:38 2021
######################################################################
TEMPLATE = app
TARGET = DoorLock
INCLUDEPATH += . "/home/pi/temp/opencv4"
###"/opt/opencv-4.1.0/include/opencv4"
# The following define makes your compiler warn you if you use any
# feature of Qt which has 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
# Input
HEADERS += Controller.h Inputs.h lcdScreen.h Outputs.h ComputerVision.h
SOURCES += Controller.cpp Inputs.cpp lcdScreen.cpp main.cpp Outputs.cpp ComputerVision.cpp
LIBS += -lpthread -lwiringPi -lopencv_core -lopencv_imgproc -lopencv_highgui -lopencv_features2d -lopencv_objdetect -lopencv_videoio
QT += core widgets
CONFIG += qt warn_on release
Note temp is a symbolic link to the correct directory