bindings: backport generator from OpenCV 4.x

- better handling of enum arguments
- less merge conflicts

modules/core/misc/python/pyopencv_umat.hpp

@@ -0,0 +1,36 @@
+#ifdef HAVE_OPENCV_CORE
+
+#include "opencv2/core/mat.hpp"
+
+typedef std::vector<Range> vector_Range;
+
+CV_PY_TO_CLASS(UMat);
+CV_PY_FROM_CLASS(UMat);
+
+static bool cv_mappable_to(const Ptr<Mat>& src, Ptr<UMat>& dst)
+{
+    //dst.reset(new UMat(src->getUMat(ACCESS_RW)));
+    dst.reset(new UMat());
+    src->copyTo(*dst);
+    return true;
+}
+
+static void* cv_UMat_queue()
+{
+    return cv::ocl::Queue::getDefault().ptr();
+}
+
+static void* cv_UMat_context()
+{
+    return cv::ocl::Context::getDefault().ptr();
+}
+
+static Mat cv_UMat_get(const UMat* _self)
+{
+    Mat m;
+    m.allocator = &g_numpyAllocator;
+    _self->copyTo(m);
+    return m;
+}
+
+#endif