Fixes for numpy2 / (Fixes #17)

* is_array_contiguous now check the array flags against c_style
* matx_to_nparray now has to specifically set the strides (otherwise numpy2 will make a bad assumption about it)

Author: pthom

cvnp/cvnp.cpp

@@ -181,15 +181,7 @@ namespace cvnp
 
     bool is_array_contiguous(const pybind11::array& a)
     {
-        pybind11::ssize_t expected_stride = a.itemsize();
-        for (int i = a.ndim() - 1; i >=0; --i)
-        {
-            pybind11::ssize_t current_stride = a.strides()[i];
-            if (current_stride != expected_stride)
-                return false;
-            expected_stride = expected_stride * a.shape()[i];
-        }
-        return true;
+        return a.flags() & pybind11::array::c_style;
     }
 
 

cvnp/cvnp.h

@@ -49,6 +49,7 @@ namespace cvnp
         return pybind11::array(
             pybind11::dtype::of<_Tp>()
             , std::vector<std::size_t> {_rows, _cols}
+            , std::vector<std::size_t>{_cols * sizeof(_Tp), sizeof(_Tp)} // Strides
             , m.val
         );
     }

cvnp/cvnp_test_helper.cpp

@@ -130,12 +130,21 @@ void display_eye(cv::Matx33d m = cv::Matx33d::eye())
 }
 
 
+cv::Matx21d RoundTripMatx21d(cv::Matx21d & m)
+{
+    //std::cout << "RoundTripMatx21d received "  << m(0, 0) << "    " << m(1, 0) << "\n";
+    return m;
+}
+
+
 
 void pydef_cvnp_test(pybind11::module& m)
 {
     m.def("make_eye", make_eye);
     m.def("display_eye", display_eye);
 
+    m.def("RoundTripMatx21d", RoundTripMatx21d);
+
     pybind11::class_<CvNp_TestHelper>(m, "CvNp_TestHelper")
         .def(pybind11::init<>())
 

tests/test_cvnp.py

@@ -139,7 +139,7 @@ def test_matx_not_shared():
     # create object
     o = CvNp_TestHelper()
 
-    m_linked = o.mx_ns                   # Make a numy array that is a copy of mx_ns *without* shared memory
+    m_linked = o.mx_ns                   # Make a numpy array that is a copy of mx_ns *without* shared memory
     assert m_linked.shape == (3, 2)      # check its shape
     m_linked[1, 1] = 3                   # a value change in the numpy array made from python
     assert o.mx_ns[1, 1] != 3            # is not visible from C++!
@@ -467,9 +467,39 @@ def test_rect():
         o.rect_double = (1, 2) # We should give 4 values!
 
 
+def test_contiguous_check():
+    # Check regression with numpy 2:
+    # See https://github.com/pthom/cvnp/issues/17
+    # The contiguous check was changed to:
+    #    bool is_array_contiguous(const pybind11::array& a) { return a.flags() & pybind11::array::c_style; }
+
+    # 1. Check contiguous matrix
+    m = np.zeros((10,10),dtype=np.uint8)
+    cvnp_roundtrip(m)
+
+    # 2. Check that a non-contiguous matrix raises an error
+    full_matrix = np.ones([10, 10], np.float32)
+    sub_matrix = full_matrix[1:5, 2:4]
+    with pytest.raises(ValueError):
+        cvnp_roundtrip(sub_matrix)
+
+
+def test_matx_roundtrip():
+    # This test was failing with numpy 2 when matx_to_nparray
+    # did not transmit the stride for small matrices (Matx)
+    from cvnp import RoundTripMatx21d
+    m = np.zeros((2, 1), np.float64)
+    m[0, 0] = 42.1
+    m[1, 0] = 43.1
+    m2 = RoundTripMatx21d(m)
+    assert are_float_close(m2[0, 0], 42.1)
+    assert are_float_close(m2[1, 0], 43.1)
+
 
 def main():
     # Todo: find a way to call pytest for this file
+    test_contiguous_check()
+    test_matx_roundtrip()
     test_refcount()
     test_mat_shared()
     test_mat__shared()