picamera2: Add support for ScalerCrops controls

Note that this change and new functionality is only applicable on Pi 5.

The stream configuration dictionary now has a "preserve_ar" key that
when set to True, will preserve the aspect ratio of the output by
cropping the sensor image appropriately. If set to False, the full
field of view of the sensor image is used to scale to the output
resolution. This happens separately for the main and lores streams.

The default behaviour of this flag is as follows:

- For the main stream, it is set to True. This preserves existing
  behaviour.

- For the lowres stream, it is set to False, which then makes the lowres
  stream crop follows the crop of the main stream. Again, this
  preservies existing behaviour, also matching VC4.

Signed-off-by: Naushir Patuck <[email protected]>

picamera2/configuration.py

@@ -83,7 +83,7 @@ def align(self, optimal=True):
 
 
 class StreamConfiguration(Configuration):
-    _ALLOWED_FIELDS = ("size", "format", "stride", "framesize")
+    _ALLOWED_FIELDS = ("size", "format", "stride", "framesize", "preserve_ar")
     _FIELD_CLASS_MAP = {}
     _FORWARD_FIELDS = {}
 

picamera2/picamera2.py

@@ -655,7 +655,7 @@ def _make_initial_stream_config(stream_config: dict, updates: dict, ignore_list=
         """
         if updates is None:
             return None
-        valid = ("format", "size", "stride")
+        valid = ("format", "size", "stride", "preserve_ar")
         for key, value in updates.items():
             if isinstance(value, SensorFormat):
                 value = str(value)
@@ -692,9 +692,9 @@ def create_preview_configuration(self, main={}, lores=None, raw={}, transform=li
         if not self._is_rpi_camera():
             raw = None
             sensor = None
-        main = self._make_initial_stream_config({"format": "XBGR8888", "size": (640, 480)}, main)
+        main = self._make_initial_stream_config({"format": "XBGR8888", "size": (640, 480), "preserve_ar": True}, main)
         self.align_stream(main, optimal=False)
-        lores = self._make_initial_stream_config({"format": "YUV420", "size": main["size"]}, lores)
+        lores = self._make_initial_stream_config({"format": "YUV420", "size": main["size"], "preserve_ar": False}, lores)
         if lores is not None:
             self.align_stream(lores, optimal=False)
         raw = self._make_initial_stream_config({"format": self.sensor_format, "size": main["size"]},
@@ -726,9 +726,10 @@ def create_still_configuration(self, main={}, lores=None, raw={}, transform=libc
         if not self._is_rpi_camera():
             raw = None
             sensor = None
-        main = self._make_initial_stream_config({"format": "BGR888", "size": self.sensor_resolution}, main)
+        main = self._make_initial_stream_config({"format": "BGR888", "size": self.sensor_resolution, "preserve_ar": True},
+                                                main)
         self.align_stream(main, optimal=False)
-        lores = self._make_initial_stream_config({"format": "YUV420", "size": main["size"]}, lores)
+        lores = self._make_initial_stream_config({"format": "YUV420", "size": main["size"], "preserve_ar": False}, lores)
         if lores is not None:
             self.align_stream(lores, optimal=False)
         raw = self._make_initial_stream_config({"format": self.sensor_format, "size": main["size"]},
@@ -760,9 +761,9 @@ def create_video_configuration(self, main={}, lores=None, raw={}, transform=libc
         if not self._is_rpi_camera():
             raw = None
             sensor = None
-        main = self._make_initial_stream_config({"format": "XBGR8888", "size": (1280, 720)}, main)
+        main = self._make_initial_stream_config({"format": "XBGR8888", "size": (1280, 720), "preserve_ar": True}, main)
         self.align_stream(main, optimal=False)
-        lores = self._make_initial_stream_config({"format": "YUV420", "size": main["size"]}, lores)
+        lores = self._make_initial_stream_config({"format": "YUV420", "size": main["size"], "preserve_ar": False}, lores)
         if lores is not None:
             self.align_stream(lores, optimal=False)
         raw = self._make_initial_stream_config({"format": self.sensor_format, "size": main["size"]},
@@ -1121,6 +1122,14 @@ def configure_(self, camera_config="preview") -> None:
         self.controls = Controls(self, controls=self.camera_config['controls'])
         self.configure_count += 1
 
+        if "ScalerCrops" in self.camera_controls:
+            par_crop = self.camera_controls["ScalerCrops"]
+            full_fov = self.camera_controls["ScalerCrop"][1]
+            scaler_crops = [par_crop[0] if camera_config["main"]["preserve_ar"] else full_fov]
+            if self.lores_index >= 0:
+                scaler_crops.append(par_crop[1] if camera_config["lores"]["preserve_ar"] else scaler_crops[0])
+            self.set_controls({"ScalerCrops": scaler_crops})
+
     def configure(self, camera_config="preview") -> None:
         """Configure the camera system with the given configuration."""
         self.configure_(camera_config)