fix: to()/array_as() same dtype-alias bug as the constructor; astype() double-cast

src/machinevisiontoolbox/ImageCore.py

@@ -1966,6 +1966,9 @@ def to(self, dtype: Dtype) -> "Image":
 
         :param dtype: Numpy data type
         :type dtype: str or NumPy dtype
+
+        |dtype_aliases|
+
         :return: image
         :rtype: :class:`Image`
 
@@ -1988,8 +1991,9 @@ def to(self, dtype: Dtype) -> "Image":
         :seealso: :meth:`astype` :meth:`to_int` :meth:`to_float`
         """
         # convert image to different type, does rescaling
-        # as just changes type
-        dtype = np.dtype(dtype)  # convert to dtype if it's a string
+        # as just changes type. array_as() and the constructor both
+        # resolve dtype (including the short-name aliases) themselves,
+        # so just pass it through unchanged rather than resolving twice.
         return self.__class__(self.array_as(dtype), dtype=dtype)
 
     def astype(self, dtype: Dtype) -> "Image":
@@ -1998,6 +2002,9 @@ def astype(self, dtype: Dtype) -> "Image":
 
         :param dtype: Numpy data type
         :type dtype: str or NumPy dtype
+
+        |dtype_aliases|
+
         :return: image
         :rtype: :class:`Image`
 
@@ -2018,6 +2025,8 @@ def astype(self, dtype: Dtype) -> "Image":
 
         :seealso: :meth:`to`
         """
+        if isinstance(dtype, str):
+            dtype = DTYPE_ALIASES.get(dtype, dtype)
         return self.__class__(self._A.astype(dtype), dtype=dtype)
 
     # ---- NumPy array access ---- #
@@ -2293,7 +2302,9 @@ def array_as(self, dtype: Dtype | None = None) -> np.ndarray:
         Convert Image to NumPy array of specified type
 
         :param dtype: data type of the output array
-        :type dtype: str or np.dtype
+        :type dtype: str or np.dtype, optional
+
+        |dtype_aliases|
         :return: NumPy array with specified type
         :rtype: ndarray(H,W) or ndarray(H,W,P)
 
@@ -2335,6 +2346,8 @@ def array_as(self, dtype: Dtype | None = None) -> np.ndarray:
         if dtype is None:
             return self._A
         else:
+            if isinstance(dtype, str):
+                dtype = DTYPE_ALIASES.get(dtype, dtype)
             dtype = np.dtype(dtype)  # convert to dtype if it's a string
             if np.issubdtype(dtype, np.integer) or np.issubdtype(dtype, np.bool_):
                 return int_image(self._A, dtype)

tests/test_dtype_resolution.py

@@ -2,8 +2,8 @@
 Consolidated dtype-resolution consistency tests.
 
 Multiple entry points resolve a user-supplied dtype string into an actual
-NumPy dtype: the Image constructor (via _infer_dtype), convert(), and (once
-fixed on their own branches) Image.to()/.array_as()/.astype() and the
+NumPy dtype: the Image constructor (via _infer_dtype), convert(), Image.to(),
+Image.array_as(), Image.astype(), and (once fixed on its own branch) the
 ImageConstantsMixin factory methods (Zeros, Constant, Random, ...). All of
 them are supposed to honour the same short-name aliases (DTYPE_ALIASES:
 'int'->uint8, 'float'->float32, 'double'->float64, 'half'->float16) plus
@@ -56,6 +56,18 @@
         arr = convert(np.ones((2, 3), dtype=np.uint8), dtype=dtype_in)
         assert arr.dtype == expected
 
+    def test_image_to(self, dtype_in, expected):
+        im = Image(np.ones((2, 3), dtype=np.uint8))
+        assert im.to(dtype_in).dtype == expected
+
+    def test_image_astype(self, dtype_in, expected):
+        im = Image(np.ones((2, 3), dtype=np.uint8))
+        assert im.astype(dtype_in).dtype == expected
+
+    def test_image_array_as(self, dtype_in, expected):
+        im = Image(np.ones((2, 3), dtype=np.uint8))
+        assert im.array_as(dtype_in).dtype == expected
+
 
 # ImageConstantsMixin factory methods: a *different* bug from the above --
 # they build their raw pixel array with the (now alias-resolved)