title: imshow error with OpenCV, Qt & Ubuntu
body: <p>I have a problem with a basic program in Qt 5.3, this is the code:</p>
  
  <p><strong>mainwindow.cpp</strong></p>
  
  <pre><code>#include "mainwindow.h"
  #include "ui_mainwindow.h"
  #include &lt;opencv2/opencv.hpp&gt;
  
  
  MainWindow::MainWindow(QWidget *parent) :
      QMainWindow(parent),
      ui(new Ui::MainWindow)
  {
      ui-&gt;setupUi(this);
      cv::Mat inputImage = cv::imread("/home/isaac/lena.jpg");
      if(!inputImage.empty()) cv::imshow("Prueba",inputImage);
  
  
  }
  
  MainWindow::~MainWindow()
  {
      delete ui;
  }
  </code></pre>
  
  <p><strong>displayimage.pro</strong></p>
  
  <pre><code>QT       += core gui
  
  greaterThan(QT_MAJOR_VERSION, 4): QT += widgets
  
  TARGET = displayimage
  TEMPLATE = app
  
  INCLUDEPATH += /usr/local/include/opencv
  LIBS += -L/usr/local/lib -lopencv_core -lopencv_imgcodecs -lopencv_highgui
  
  SOURCES += main.cpp\
      mainwindow.cpp
  
  HEADERS  += mainwindow.h
  
  FORMS    += mainwindow.ui
  </code></pre>
  
  <p>This is the output error:</p>
  
  <pre><code>Starting /home/isaac/workspace/Qt Creator/Prueba/build-displayimage-Desktop_Qt_5_5_0_GCC_64bit-Release/displayimage...
  The program has unexpectedly finished.
  /home/isaac/workspace/Qt Creator/Prueba/build-displayimage-Desktop_Qt_5_5_0_GCC_64bit-Release/displayimage crashed
  </code></pre>
  
  <p>I just read an image and show but does not work and don't know why . If I comment imshow the program works.</p>