map 64bit int anf bfloat16

modules/python/src2/cv2_numpy.cpp

@@ -34,6 +34,14 @@ UMatData* NumpyAllocator::allocate(int dims0, const int* sizes, int type, void*
 
     int depth = CV_MAT_DEPTH(type);
     int cn = CV_MAT_CN(type);
+    // cvDepthToNumpyType() widens CV_16BF to NPY_FLOAT for export, which is only
+    // valid when the values are converted (see pyopencv_from). Backing a CV_16BF
+    // Mat with a float32 buffer here would instead pair a 2-byte element step with
+    // 4-byte NumPy strides and silently corrupt the data, so refuse it outright.
+    if( depth == CV_16BF )
+        CV_Error(Error::StsNotImplemented,
+                 "CV_16BF (bfloat16) arrays cannot be allocated through the NumPy allocator: "
+                 "NumPy has no bfloat16 dtype");
     int typenum = cvDepthToNumpyType(depth);
     int i, dims = dims0;
     cv::AutoBuffer<npy_intp> _sizes(dims + 1);