title: Use GPU with opencv-python
body: <p>I'm trying to use opencv-python with GPU on windows 10.</p>
  <p>I installed opencv-contrib-python using pip and it's v4.4.0.42, I also have Cuda on my computer and in path.</p>
  <p>Anyway, here is a (simple) code that I'm trying to compile:</p>
  <pre><code>import cvlib as cv
  from cvlib.object_detection import draw_bbox
  
  bbox, label, conf = cv.detect_common_objects(img,confidence=0.5,model='yolov3-worker',enable_gpu=True)
  
  output_image = draw_bbox(img, bbox, label, conf)
  </code></pre>
  <p>First, here is the line that tell me that tf is ok with cuda:</p>
  <pre><code>2020-08-26 5:51:55.718555: I tensorflow/stream_executor/platform/default/dso_loader.cc:48] Successfully opened dynamic library cudart64_101.dll
  </code></pre>
  <p>but when I try to use my GPU to analyse the image, here is what happen:</p>
  <pre><code>[ WARN:0] global C:\Users\appveyor\AppData\Local\Temp\1\pip-req-build-j8nxabm_\opencv\modules\dnn\src\dnn.cpp (1429) cv::dnn::dnn4_v20200609::Net::Impl::setUpNet DNN module was not built with CUDA backend; switching to CPU
  </code></pre>
  <p>Is there a way to solve this without install opencv using cmake? It's a mess on windows...</p>