Opencv 3.0 - erode is not a member of gpu namespace

edit

The gpu module was redesigned in OpenCV 3.0. It was splitted onto several modules, it was renamed to cuda and gpu:: namespace was renamed to cuda::. All filters were moved to opencv_cudafilters module. Also all single-function filters were removed, now only cv::Ptr<cv::cuda::Filter> object can be used:

cv::Ptr<cv::cuda::Filter> erode = cv::cuda::createMorphologyFilter(cv::MORPH_ERODE, src.type(), kernel);
erode->apply(src, dst);