Update ImageCanvasItem.py

Fixed some more type errors.

nion/swift/ImageCanvasItem.py

@@ -1143,18 +1143,19 @@ def convert_pixel_to_normalised(self, coord: Geometry.IntPoint) -> Geometry.Floa
                                                          list())
             if widget_mapping:
                 mapped = self.map_widget_to_image(coord)
-                norm_coord = tuple(ele1 / ele2 for ele1, ele2 in zip(mapped, self.__data_shape))
+                norm_coord = tuple(ele1 / ele2 for ele1, ele2 in zip(iter(mapped), iter(self.__data_shape)))
                 return Geometry.FloatPoint(norm_coord[0], norm_coord[1])  # y,x
+        return Geometry.FloatPoint(-1, -1)
 
     #Apply a zoom factor to the widget, optionally focussed on a specific point
-    def _apply_fixed_zoom(self, zoom_in: bool, coord: Geometry.IntPoint = None) -> None:
+    def _apply_fixed_zoom(self, zoom_in: bool, coord: typing.Optional[Geometry.IntPoint]) -> None:
         if coord:
             # Coordinate specified, so needing to recenter to that point before we adjust zoom levels
             widget_mapping = ImageCanvasItemMapping.make(self.__data_shape, self.__composite_canvas_item.canvas_bounds, list())
             if widget_mapping:
                 mapped = self.map_widget_to_image(coord)
-                norm_coord = tuple(ele1 / ele2 for ele1, ele2 in zip(mapped, self.__data_shape))
-                self._set_image_canvas_position(norm_coord)
+                norm_coord = tuple(ele1 / ele2 for ele1, ele2 in zip(iter(mapped), iter(self.__data_shape)))
+                self._set_image_canvas_position(Geometry.FloatPoint(norm_coord[0], norm_coord[1]))
 
                 # ensure that at least half of the image is always visible
                 new_image_norm_center_0 = max(min(norm_coord[0], 1.0), 0.0)
@@ -1175,15 +1176,15 @@ def _apply_selection_zoom(self, coord1: Geometry.IntPoint, coord2: Geometry.IntP
         if widget_mapping:
             coord1_mapped = self.map_widget_to_image(coord1)
             coord2_mapped = self.map_widget_to_image(coord2)
-            norm_coord1 = tuple(ele1 / ele2 for ele1, ele2 in zip(coord1_mapped, self.__data_shape))
-            norm_coord2 = tuple(ele1 / ele2 for ele1, ele2 in zip(coord2_mapped, self.__data_shape))
+            norm_coord1 = tuple(ele1 / ele2 for ele1, ele2 in zip(iter(coord1_mapped), iter(self.__data_shape)))
+            norm_coord2 = tuple(ele1 / ele2 for ele1, ele2 in zip(iter(coord2_mapped), iter(self.__data_shape)))
 
-            norm_coord = tuple((ele1 + ele2)/2 for ele1, ele2 in zip(norm_coord1, norm_coord2))
-            self._set_image_canvas_position(norm_coord)
+            norm_coord = tuple((ele1 + ele2)/2 for ele1, ele2 in zip(iter(norm_coord1), iter(norm_coord2)))
+            self._set_image_canvas_position(Geometry.FloatPoint(norm_coord[0], norm_coord[1]))
             # image now centered on middle of selection, need to calculate new zoom level required
             # selection size in widget pixels
             selection_size_screen_space = tuple(
-                abs(ele1 - ele2) for ele1, ele2 in zip(coord1, coord2))  # y,x
+                abs(ele1 - ele2) for ele1, ele2 in zip(iter(coord1), iter(coord2)))  # y,x
             widget_width = self.__composite_canvas_item.canvas_bounds.width / self.__image_zoom
             widget_height = self.__composite_canvas_item.canvas_bounds.height / self.__image_zoom
             widget_width_factor = widget_width / selection_size_screen_space[1]