[SOLVED][ERROR] [HELP] Using Qt + OpenCV to get what does webcam see

SGaist

Hi,

Did you start you project from a QMainWindow and then changed manually the class to a QDialog ?

YDYD

Hi.
For dialog I din change. But I change the cameradevice to QObject

SGaist

How did you create your dialog ?

YDYD

Qt GUI application. Qmainwindow

SGaist

Then how did it become a QDialog ?

YDYD

errr, I changed the QMainwindow to QDialog manually, i should use QMainwindow or QDialog to create Dialog class?

YDYD

[UPDATE]
After correction, I get another error as following:

ERROR
@pi@raspberrypi:~/qt/Dialog$ qmake -project
pi@raspberrypi:~/qt/Dialog$ qmake Dialog.pro
pi@raspberrypi:~/qt/Dialog$ make
g++ -Wl,-O1 -o Dialog cameradevice.o dialog.o main.o moc_cameradevice.o moc_dialog.o -L/usr/lib/arm-linux-gnueabihf -lQtGui -lQtCore -lpthread
cameradevice.o: In function CameraDevice::CameraDevice(QObject*)': cameradevice.cpp:(.text+0x24): undefined reference to cv::VideoCapture::VideoCapture()'
cameradevice.o: In function cv::Mat::~Mat()': cameradevice.cpp:(.text._ZN2cv3MatD2Ev[_ZN2cv3MatD5Ev]+0x70): undefined reference to cv::fastFree(void*)'
cameradevice.cpp:(.text._ZN2cv3MatD2Ev[_ZN2cv3MatD5Ev]+0x7c): undefined reference to `cv::Mat::deallocate()'
collect2: ld returned 1 exit status
make: *** [Dialog] Error 1@

Jeroentjehome

The error is because the CameraDevice class is unable to find the cv class when calling it's static member function: VideoCapture. What type of library do you include? Or do you use the QLibrary for that??

YDYD

i include

highgui
cv
cxcore

YDYD

From my knowledge,

VideoCapture is under highgui.hpp.

i have include this file already.

anyone knwo what is happening?

SGaist

You are not linking to the OpenCV libraries

YDYD

Do you mean in XXX.pro file ?

SGaist

Yes indeed, in you project pro file

YDYD

@OPENCV_PATH = /usr/local/include/opencv2/
LIBS_PATH = /usr/local/include/opencv/
LIBS += -L$$LIBS_PATH
-lcv
-lhighgui
-lcxcore

INCLUDEPATH += $$OPENCV_PATH/core
$$OPENCV_PATH/highgui/@

This is how my linking look like

SGaist

Are you sure you are linking to all the needed libraries ?

YDYD

no, i am nt sure, but i checked many times if i left out any.
Should not be left out...
if this is not left out of libraries, what is the problem ?

SGaist

Just a missing library. You can check with pkg-config what you need. You can even use it within your pro file (have a look at qmake's documentation)

YDYD

Ok. I give it a try and looh. Thx a lot SGaist

YDYD

[quote author="SGaist" date="1403731430"]Just a missing library. You can check with pkg-config what you need. You can even use it within your pro file (have a look at qmake's documentation) [/quote]

Don't really know how to do....
I just have a look at the qmake genarated makefile. The INCPATH inside should be the openCV path ? It is different.
the another thing to mention is, after i qmake project, my Dialog.pro file will changed. the coding will all replaced.

i am new to Qt and OpenCV, i just could not link them up.

Thanks to SGaist again,

YDYD

Hi SGaist,

Finally I did it!

I make a slightly change in "qmake.conf" file which is under @/usr/share/qt4/mkspecs/default/qmake.conf@

I added in the INCLUDEPATH and LIBS.
Then it Works!!