title: Qt Creator LNK2019:Unresolved external symbol using OpenCV
body: <p>I've been trying to compile a project for the past two days in <code>Qt</code> using <code>OpenCV</code> but can't figure out why it doesn't. My application has only <code>main.cpp</code>, <code>widget.cpp</code> and <code>widget.h</code></p>
  
  <p>here is my .pro file</p>
  
  <pre><code>  QT       += core gui opengl
    greaterThan(QT_MAJOR_VERSION, 4): QT += widgets
  
    TARGET = FaceDetect
    TEMPLATE = app
    SOURCES += main.cpp\
               widget.cpp
  
    HEADERS  += widget.h
  
    FORMS    += widget.ui
  
    INCLUDEPATH += C:/opencv/build/include/
    LIBS += -LC:/opencv/build/x64/vc10/lib/
             -libopencv_core2410
             -libopencv_highgui2410
             -libopencv_imgproc2410
             -libopencv_features2d2410
              -libopencv_calib3d24610
  </code></pre>
  
  <p>and these are the errors I keep getting:    </p>
  
  <pre><code>main.obj:-1: error: LNK2019: unresolved external symbol "public: void __thiscall cv::Mat::deallocate(void)" (?deallocate@Mat@cv@@QAEXXZ) referenced in function "public: void __thiscall cv::Mat::release(void)" (?release@Mat@cv@@QAEXXZ)    
  
  moc_widget.obj:-1: error: LNK2001: unresolved external symbol "public: void __thiscall cv::Mat::deallocate(void)" (?deallocate@Mat@cv@@QAEXXZ)
  
  moc_widget.obj:-1: error: LNK2001: unresolved external symbol "public: void __thiscall cv::Mat::deallocate(void)" (?deallocate@Mat@cv@@QAEXXZ)
  </code></pre>
  
  <p>Can anyone explain why and how I an get rid of these please?</p>
  
  <p>Thanks!</p>