fix types in _zero_preserving_modulo_seq to proper function dispatch

src/PartSegCore_compiled_backend/_napari_mapping.pyx

@@ -28,7 +28,7 @@ ctypedef fused out_types:
     out_types_mod
     cnp.float32_t
 
-def _zero_preserving_modulo_seq(label_types[:] labels,  out_types_mod modulo, label_types to_zero, out_types_mod[:] out):
+def _zero_preserving_modulo_seq(label_types[:] labels,  int modulo, int to_zero, out_types_mod[:] out):
     cdef Py_ssize_t i
     cdef Py_ssize_t n = labels.shape[0]
     for i in range(n):
@@ -37,7 +37,7 @@ def _zero_preserving_modulo_seq(label_types[:] labels,  out_types_mod modulo, la
         else:
             out[i] = ((modulo + ((labels[i] - 1) % modulo)) % modulo) + 1
 
-def _zero_preserving_modulo_par(label_types[:] labels, out_types_mod modulo, label_types to_zero, out_types_mod[:] out):
+def _zero_preserving_modulo_par(label_types[:] labels, int modulo, int to_zero, out_types_mod[:] out):
     cdef Py_ssize_t i
     cdef Py_ssize_t n = labels.shape[0]
     for i in prange(n, nogil=True):

src/tests/test_napari_mapping.py

@@ -57,3 +57,16 @@ def test_map_array(func, data):
     out = func(data, map_dkt, 0)
     assert out.dtype == np.uint8
     npt.assert_array_equal(out, _map_array(data, map_dkt, np.uint8))
+
+
+@pytest.mark.parametrize('num,dtype', [(40, np.uint8), (1000, np.uint16)])
+@pytest.mark.parametrize('func', [zero_preserving_modulo_parallel, zero_preserving_modulo_sequential])
+def test_cast_labels_to_minimum_type_auto(num: int, dtype, monkeypatch, func):
+    data = np.zeros(3, dtype=np.uint32)
+    data[1] = 10
+    data[2] = 10**6 + 5
+    cast_arr = func(data, num, 0)
+    assert cast_arr.dtype == dtype
+    assert cast_arr[0] == 0
+    assert cast_arr[1] == 10
+    assert cast_arr[2] == 10**6 % num + 5