Include OpenCV library into a project.

[jenya7]

I installed OpenCV

sudo apt-get install libopencv-dev

Now I open a project and in main.cpp include

 #include "opencv2/opencv.hpp"

Qt sees the directory and files in it. But when I compile I get a lot of errors in the opencv library files. Why?
May be I should include it in the *.pro file - LIB+= ????? - what should I include?

[jsulm]

@jenya7 said in Include OpenCV library into a project.:

May be I should include it in the *.pro file - LIB+= ?

Yes.
"what should I include?" - all OpenCV libs you're using.
Which libs exactly you can deduce from the error messages and then checking OpenCV documentation.

[jenya7]

The errors I get

-1: error: main.o: in function cv::String::~String()': -1: error: main.o: in function cv::String::operator=(cv::String const&)' :/usr/include/opencv2/core/cvstd.hpp:672: error: undefined reference to `cv::String::deallocate()' -1: error: collect2: error: ld returned 1 exit status

What exactly I should include? In usr/include/ I see opencv2 folder with a lot of folders and files in it.

I found the solution

LIBS += -lopencv_core -lopencv_imgproc -lopencv_imgcodecs

Now I’m facing another problem - Build is OK but when I run I get

qt5ct: using qt5ct plugin
GLib-GObject-WARNING **: 11:53:16.119: cannot register existing type ‘GtkWidget’
GLib-GObject-CRITICAL **: 11:53:16.119: g_type_add_interface_static: assertion ‘G_TYPE_IS_INSTANTIATABLE (instance_type)’ failed
GLib-GObject-WARNING **: 11:53:16.119: cannot register existing type ‘GtkBuildable’
GLib-GObject-CRITICAL **: 11:53:16.119: g_type_interface_add_prerequisite: assertion ‘G_TYPE_IS_INTERFACE (interface_type)’ failed
GLib-CRITICAL **: 11:53:16.119: g_once_init_leave: assertion ‘result != 0’ failed
GLib-GObject-CRITICAL **: 11:53:16.119: g_type_add_interface_static: assertion ‘G_TYPE_IS_INSTANTIATABLE (instance_type)’ failed
GLib-GObject-CRITICAL **: 11:53:16.119: g_type_register_static: assertion ‘parent_type > 0’ failed

I found a fix
sudo nano /etc/xdg/qt5ct/qt5ct.conf
replace style=gtk2 with style=gtk3