Apply suggestions from code review of branch jpeg-capture-in-stacking

Co-authored-by: Beth Probert <beth_probert@outlook.com>

src/openflexure_microscope_server/things/autofocus.py

@@ -294,6 +294,7 @@ class AutofocusThing(Thing):
 
         stack_z_range = stack_dz * (images_to_capture - 1)
         if stack_z_range > 0:
+            # Perform backlash corrected move. See issue #420
             stage.move_relative(z=-(STACK_OVERSHOOT + stack_z_range / 2))
             stage.move_relative(z=STACK_OVERSHOOT)
         time.sleep(0.3)
@@ -348,7 +349,7 @@ class AutofocusThing(Thing):
         images_dir: str,
         stack_dir: str,
         logger: InvocationLogger,
-    ):
+    ) -> None:
         """Gets a list of images in a folder (stack_dir), sorts them by filesize, and copies the sharpest
         image to images dir."""
         image_list = glob.glob(os.path.join(stack_dir, "*"))

src/openflexure_microscope_server/things/camera/__init__.py

@@ -31,6 +31,8 @@ class JPEGBlob(Blob):
 
 
 class PNGBlob(Blob):
+    """A class representing a PNG image as a LabThings FastAPI Blob"""
+
     media_type: str = "image/png"
 
 

src/openflexure_microscope_server/things/smart_scan.py

@@ -377,10 +377,13 @@ class SmartScanThing(Thing):
         return (next_point[0], next_point[1], z_estimate)
 
     @_scan_running
-    def _calc_displacement_from_test_image(self, overlap):
+    def _calc_displacement_from_test_image(self, overlap: int) -> tuple[int, int]:
         """
         Take a test image and use camera stage mapping to calculate x and y displacement
 
+        :param overlap: The desired overlap as a fraction of the image. i.e. 0.5 means
+        that each image should overlap its nearest neighbour by 50%.
+
         Return (dx, dy) - the x and y displacments in steps
         """
         test_jpg = self._cam.grab_jpeg()
@@ -422,7 +425,9 @@ class SmartScanThing(Thing):
         dx, dy = self._calc_displacement_from_test_image(overlap)
         stitch_resize = STITCHING_RESOLUTION[0] / self.capture_resolution[0]
 
-        self._scan_logger.debug(f"Resizing images when stitching by {stitch_resize}")
+        self._scan_logger.debug(
+            f"Resizing images when stitching by a factor of {stitch_resize}"
+        )
 
         self._scan_logger.info(
             f"Based on an overlap of {overlap}, we will make steps of {dx}, {dy}"