use opencv-python with GPU

来源：https://forum.opencv.org/t/can-i-use-opencv-python-with-gpu/8947/2

most opencv functions are opencl optimized, and you can access them using cv2.UMat out of the box.

if you do need CUDA, you will have to build your cv2 from src (this will ofc need nvidia hw and a CUDA sdk installed)

!git clone https://github.com/opencv/opencv
!git clone https://github.com/opencv/opencv_contrib
!mkdir /content/build
%cd /content/build

!cmake -DOPENCV_EXTRA_MODULES_PATH=/content/opencv_contrib/modules  \
       -DBUILD_SHARED_LIBS=OFF \
       -DBUILD_TESTS=OFF \
       -DBUILD_PERF_TESTS=OFF \
       -DBUILD_EXAMPLES=OFF \
       -DWITH_OPENEXR=OFF \
       -DWITH_CUDA=ON \
       -DWITH_CUBLAS=ON \
       -DWITH_CUDNN=ON \
       -DOPENCV_DNN_CUDA=ON \
       /content/opencv

!make -j8 install