also the mask is transformed during alignment

brainglobe_template_builder/napari/align_widget.py

@@ -146,18 +146,28 @@ def _on_estimate_button_click(self):
         show_info("Please move all 9 estimated points exactly to the midplane")
 
     def _on_align_button_click(self):
-        """Align image and add the transformed image to the viewer."""
+        """Align image and mask to midplane and add them to the viewer."""
         image_name = self.select_image_dropdown.currentText()
+        image_data = self.viewer.layers[image_name].data
+        mask_name = self.select_mask_dropdown.currentText()
+        mask_data = self.viewer.layers[mask_name].data
         points_name = self.select_points_dropdown.currentText()
+        points_data = self.viewer.layers[points_name].data
         axis = self.select_axis_dropdown.currentText()
 
         aligner = MidplaneAligner(
-            self.viewer.layers[image_name].data,
-            self.viewer.layers[points_name].data,
+            image_data,
+            points_data,
             symmetry_axis=axis,
         )
-        aligned_image = aligner.transform_image()
-        self.viewer.add_image(aligned_image, name="aligned image")
+        aligned_image = aligner.transform_image(image_data)
+        self.viewer.add_image(aligned_image, name="aligned_image")
+        aligned_mask = aligner.transform_image(mask_data)
+        self.viewer.add_labels(aligned_mask, name="aligned_mask", opacity=0.5)
+        # Hide original image, mask, and points layers
+        self.viewer.layers[image_name].visible = False
+        self.viewer.layers[mask_name].visible = False
+        self.viewer.layers[points_name].visible = False
 
     def _on_dropdown_selection_change(self):
         # Enable estimate button if mask dropdown has a value

brainglobe_template_builder/preproc/alignment.py

@@ -153,7 +153,7 @@ def _fit_plane_to_points(self):
         self.normal_vector = normal_vector
         self.symmetry_axis_vector = symmetry_axis_vector
 
-    def get_transform(self):
+    def _compute_transform(self):
         """Find the transformation matrix that aligns the plane defined by the
         points to the midplane of the image along the symmetry axis.
         """
@@ -179,11 +179,19 @@ def get_transform(self):
         self.transform = (
             translation_to_mid_axis @ rotation @ translation_to_origin
         )
-        return self.transform
 
-    def transform_image(self):
-        """Transform the image using the transformation matrix."""
+    def transform_image(self, image: np.ndarray = None):
+        """Transform the image using the transformation matrix.
+
+        Parameters
+        ----------
+        image : np.ndarray
+            The image to transform. If None, the image passed to the
+            constructor is used.
+        """
         if not hasattr(self, "transform"):
-            self.get_transform()
-        self.transformed_image = apply_transform(self.image, self.transform)
+            self._compute_transform()
+        if image is None:
+            image = self.image
+        self.transformed_image = apply_transform(image, self.transform)
         return self.transformed_image