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

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  • SGaistS Offline
    SGaistS Offline
    SGaist
    Lifetime Qt Champion
    wrote on last edited by
    #6

    Then how did it become a QDialog ?

    Interested in AI ? www.idiap.ch
    Please read the Qt Code of Conduct - https://forum.qt.io/topic/113070/qt-code-of-conduct

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    • Y Offline
      Y Offline
      YDYD
      wrote on last edited by
      #7

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

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      • Y Offline
        Y Offline
        YDYD
        wrote on last edited by
        #8

        [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@

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        • JeroentjehomeJ Offline
          JeroentjehomeJ Offline
          Jeroentjehome
          wrote on last edited by
          #9

          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??

          Greetz, Jeroen

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          • Y Offline
            Y Offline
            YDYD
            wrote on last edited by
            #10

            i include

            1. highgui
            2. cv
            3. cxcore
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            • Y Offline
              Y Offline
              YDYD
              wrote on last edited by
              #11

              From my knowledge,

              VideoCapture is under highgui.hpp.

              i have include this file already.

              anyone knwo what is happening?

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              • SGaistS Offline
                SGaistS Offline
                SGaist
                Lifetime Qt Champion
                wrote on last edited by
                #12

                You are not linking to the OpenCV libraries

                Interested in AI ? www.idiap.ch
                Please read the Qt Code of Conduct - https://forum.qt.io/topic/113070/qt-code-of-conduct

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                • Y Offline
                  Y Offline
                  YDYD
                  wrote on last edited by
                  #13

                  Do you mean in XXX.pro file ?

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                  • SGaistS Offline
                    SGaistS Offline
                    SGaist
                    Lifetime Qt Champion
                    wrote on last edited by
                    #14

                    Yes indeed, in you project pro file

                    Interested in AI ? www.idiap.ch
                    Please read the Qt Code of Conduct - https://forum.qt.io/topic/113070/qt-code-of-conduct

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                    • Y Offline
                      Y Offline
                      YDYD
                      wrote on last edited by
                      #15

                      @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

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                      • SGaistS Offline
                        SGaistS Offline
                        SGaist
                        Lifetime Qt Champion
                        wrote on last edited by
                        #16

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

                        Interested in AI ? www.idiap.ch
                        Please read the Qt Code of Conduct - https://forum.qt.io/topic/113070/qt-code-of-conduct

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                        • Y Offline
                          Y Offline
                          YDYD
                          wrote on last edited by
                          #17

                          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 ?

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                          • SGaistS Offline
                            SGaistS Offline
                            SGaist
                            Lifetime Qt Champion
                            wrote on last edited by
                            #18

                            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)

                            Interested in AI ? www.idiap.ch
                            Please read the Qt Code of Conduct - https://forum.qt.io/topic/113070/qt-code-of-conduct

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                            • Y Offline
                              Y Offline
                              YDYD
                              wrote on last edited by
                              #19

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

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                              • Y Offline
                                Y Offline
                                YDYD
                                wrote on last edited by
                                #20

                                [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,

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                                • Y Offline
                                  Y Offline
                                  YDYD
                                  wrote on last edited by
                                  #21

                                  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!!

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                                  • SGaistS Offline
                                    SGaistS Offline
                                    SGaist
                                    Lifetime Qt Champion
                                    wrote on last edited by
                                    #22

                                    Don't modify that file, that will make all your projects link to OpenCV. Just correct your pro file with what you added there.

                                    Interested in AI ? www.idiap.ch
                                    Please read the Qt Code of Conduct - https://forum.qt.io/topic/113070/qt-code-of-conduct

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                                    • Y Offline
                                      Y Offline
                                      YDYD
                                      wrote on last edited by
                                      #23

                                      Hi SGaist,

                                      I don't get what you mean,
                                      Showing what camera get is only a part i need to do,

                                      I need openCV in my whole project, I need to do a Robot Vision System GUI,
                                      so, I still not suggested to modify that file?

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                                      • SGaistS Offline
                                        SGaistS Offline
                                        SGaist
                                        Lifetime Qt Champion
                                        wrote on last edited by
                                        #24

                                        Modifying /usr/share/qt4/mkspecs/default/qmake.conf means that every new project you'll create will be linked to OpenCV which is not a good idea.

                                        Just move what you added in qmake.conf in your project's pro file

                                        Interested in AI ? www.idiap.ch
                                        Please read the Qt Code of Conduct - https://forum.qt.io/topic/113070/qt-code-of-conduct

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                                        • SurajS Offline
                                          SurajS Offline
                                          Suraj
                                          wrote on last edited by
                                          #25

                                          Dear YDYD sir,
                                          i am new in QT. I also want to start a camera and want a image capturing and video recording functionality. I already triend the example which is given on official webside. But it showing multiple errors in header file. consider there are two header file. first is "one.h" and second is "second.h". In one.h,second.h is included. One.h is included in my application. At first it gives error for one.h. For solving this error i locate that file and add it in "#include </path/one.h>" then it solve the problem. But it shows error for second.h and header files which is included in that. One time i add path for all this error. It solves it but it then shows error in the functions of this header file. Sir i dont know what to do now. So can you send me the demo application to me to my mail id "dangat123suraj@gmail.com" and suggest solution for this problem. Thanking you in advance.

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