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

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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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