Capture metadata with more info, including default time tags

src/openflexure_microscope_server/things/camera/__init__.py

@@ -288,10 +288,12 @@ class BaseCamera(lt.Thing):
 
         img = self.capture_image(stream_name, wait)
 
+        capture_metadata = self._capture_metadata(metadata_getter())
+
         self._save_capture(
             jpeg_path=jpeg_path,
             image=img,
-            metadata=metadata_getter(),
+            metadata=capture_metadata,
             logger=logger,
         )
 
@@ -388,7 +390,7 @@ class BaseCamera(lt.Thing):
         :param save_resolution: can be set to resize the image before saving. By
             default this is None meaning that the image is saved at original resolution.
         """
-        image, metadata = self._robust_image_capture(
+        image, capture_metadata = self._robust_image_capture(
             metadata_getter,
             logger=logger,
         )
@@ -396,7 +398,7 @@ class BaseCamera(lt.Thing):
         self._save_capture(
             jpeg_path,
             image,
-            metadata,
+            capture_metadata,
             logger,
             save_resolution,
         )
@@ -476,14 +478,63 @@ class BaseCamera(lt.Thing):
         for capture_attempts in range(5):
             try:
                 metadata = metadata_getter()
+                capture_metadata = self._capture_metadata(metadata)
+
                 image = self.capture_image(stream_name="main", wait=5)
-                return image, metadata
+                return image, capture_metadata
             except TimeoutError:
                 logger.warning(
                     f"Attempt {capture_attempts + 1} to capture image timed out. Do you have enough RAM?"
                 )
         raise CaptureError("An error occurred while capturing after 5 attempts")
 
+    def _capture_metadata(
+        self,
+        metadata: dict,
+    ) -> None:
+        """Return the metadata for a capture, from the thing states, time and known names."""
+        return {
+            "capture_time": datetime.now().timestamp(),
+            "make": "OpenFlexure",
+            "model": "OpenFlexure Microscope",
+            "things_states": metadata,
+        }
+
+    def _add_metadata_to_capture(self, jpeg_path: str, capture_metadata: dict) -> None:
+        """Add the EXIF metadata for a JPEG image.
+
+        This adds:
+        - UserComment (JSON-encoded metadata from the Things)
+        - Capture time (DateTimeOriginal, DateTimeDigitized, 0th DateTime)
+        - Camera Make and Model
+        """
+        # Load existing EXIF
+        exif_dict = piexif.load(jpeg_path)
+
+        user_metadata = capture_metadata["things_states"]
+        capture_time = capture_metadata["capture_time"]
+
+        # Update UserComment with JSON-encoded metadata
+        exif_dict["Exif"][piexif.ExifIFD.UserComment] = json.dumps(
+            user_metadata
+        ).encode("utf-8")
+
+        capture_time_str = datetime.fromtimestamp(capture_time).strftime(
+            "%Y:%m:%d %H:%M:%S"
+        )
+
+        # Update all relevant EXIF date fields
+        exif_dict["Exif"][piexif.ExifIFD.DateTimeOriginal] = capture_time_str
+        exif_dict["Exif"][piexif.ExifIFD.DateTimeDigitized] = capture_time_str
+        exif_dict["0th"][piexif.ImageIFD.DateTime] = capture_time_str
+
+        # Update Make and Model
+        exif_dict["0th"][piexif.ImageIFD.Make] = capture_metadata["make"]
+        exif_dict["0th"][piexif.ImageIFD.Model] = capture_metadata["model"]
+
+        # Write the updated EXIF back to the file
+        piexif.insert(piexif.dump(exif_dict), jpeg_path)
+
     def _save_capture(
         self,
         jpeg_path: str,
@@ -512,12 +563,7 @@ class BaseCamera(lt.Thing):
             # disabled, file size increases and quality is barely or not affected
             image.save(jpeg_path, quality=95, subsampling=0)
             try:
-                # Load EXIF metadata from image so it can be added to.
+                self._add_metadata_to_capture(jpeg_path, metadata)
-                exif_dict = piexif.load(jpeg_path)
-                exif_dict["Exif"][piexif.ExifIFD.UserComment] = json.dumps(
-                    metadata
-                ).encode("utf-8")
-                piexif.insert(piexif.dump(exif_dict), jpeg_path)
             except Exception:
                 # We need to capture any exception as there are many reasons metadata
                 # might not be added. We warn rather than log the error.
@@ -652,8 +698,8 @@ class BaseCamera(lt.Thing):
 
     @property
     def thing_state(self) -> Mapping[str, Any]:
-        """Summary metadata describing the current state of the Thing."""
+        """Empty metadata dict for subclasses to populate."""
-        return {"capture_time": time.time()}
+        return {}
 
 
 CameraDependency = lt.deps.direct_thing_client_dependency(BaseCamera, "/camera/")