title: OpenCV: No GPU support (The library is compiled without CUDA support)
body: <p>I installed opencv 2.4.6.1 with cmake and with option WITH_CUDA=ON.
  I tryed some samples code and it worked well.
  But some trouble lies with gpu library.
  I add in the source file: </p>
  
  <pre><code>cv::gpu::printShortCudaDeviceInfo(cv::gpu::getDevice());</code></pre>
  
  <p>And it returned: 
  <code>OpenCV Error: No GPU support (The library is compiled without CUDA support) in getDevice, file /build/buildd/opencv-2.4.2+dfsg/modules/core/src/gpumat.cpp, line 182 terminate called after throwing an instance of 'cv::Exception' what(): /build/buildd/opencv-2.4.2+dfsg/modules/core/src/gpumat.cpp:182: error: (-216) The library is compiled without CUDA support in function getDevice
  </code>
  How could I fix it?</p>