How to correctly add an OpenCV build to a QT application

[mikeitexpert]

I am compiling a Qt Quick QML project with opencv 4.0 used in it on Unbuntu 18.

I build the opencv 4 from source.

I also have an OpenCv 3.2 installed from ubuntu's repository.

To ensure it is actually using Opencv 4.0 I created an opencv.pri file as below:

INCLUDEPATH += -I/home/mike/opencv-4.0.1/
LIBS += -L/home/mike/opencv-4.0.1/build -lopencv_calib3d -lopencv_core -lopencv_features2d -lopencv_flann -lopencv_highgui -lopencv_imgcodecs -lopencv_imgproc -lopencv_ml -lopencv_objdetect -lopencv_photo -lopencv_stitching -lopencv_videoio -lopencv_video

But if I remove "-L/home/mike/opencv-4.0.1/build" from above the code still compiles.

Does that mean it is using OpenCv 4 headers/includes and libraries from Opencv 3.2.

How else QT looks for libraries directory?

Thank you

[aha_1980]

hi @mikeitexpert,

How else QT looks for libraries directory?

Qt (and not QT, that is QuickTime) doesn't look for directories. It's the Linker doing that, and linking on Linux is complicated.*) You can google that up, there are multiple fallbacks taken in account when doing that.

Does that mean it is using OpenCv 4 headers/includes and libraries from Opencv 3.2.

Most likely, yes.

Regards

*) Well, on Windows it's not better, hence called the DLL hell. Good libraries are therefore versioned (like Qt)