Copy optimisations for JpegEncder

Also add a YUV capture test for both JpegEncoder and still JPEG
capture.

Signed-off-by: David Plowman <david.plowman@raspberrypi.com>

picamera2/encoders/jpeg_encoder.py

@@ -4,6 +4,7 @@
 
 from picamera2.encoders import Quality
 from picamera2.encoders.multi_encoder import MultiEncoder
+from picamera2.request import MappedArray
 
 
 class JpegEncoder(MultiEncoder):
@@ -42,11 +43,19 @@ def encode_func(self, request, name):
         :return: Jpeg image
         :rtype: bytes
         """
-        if self.colour_space is None:
-            self.colour_space = self.FORMAT_TABLE[request.config[name]["format"]]
-        array = request.make_array(name)
-        return simplejpeg.encode_jpeg(array, quality=self.q, colorspace=self.colour_space,
-                                      colorsubsampling=self.colour_subsampling)
+        fmt = request.config[name]["format"]
+        with MappedArray(request, name) as m:
+            if fmt == "YUV420":
+                width, height = request.config[name]['size']
+                Y = m.array[:height, :width]
+                reshaped = m.array.reshape((m.array.shape[0] * 2, m.array.strides[0] // 2))
+                U = reshaped[2 * height: 2 * height + height // 2, :width // 2]
+                V = reshaped[2 * height + height // 2:, :width // 2]
+                return simplejpeg.encode_jpeg_yuv_planes(Y, U, V, self.q)
+            if self.colour_space is None:
+                self.colour_space = self.FORMAT_TABLE[request.config[name]["format"]]
+            return simplejpeg.encode_jpeg(m.array, quality=self.q, colorspace=self.colour_space,
+                                          colorsubsampling=self.colour_subsampling)
 
     def _setup(self, quality):
         # If an explicit quality was specified, use it, otherwise try to preserve any q value

picamera2/request.py

@@ -203,7 +203,7 @@ def save(self, name: str, file_output: Any, format: Optional[str] = None,
         config = self.config.get(name, None)
         if config is None:
             raise RuntimeError(f'Stream {name!r} is not defined')
-        if self.FASTER_JPEG and config['format'] != "MJPEG" and \
+        if (config['format'] == 'YUV420' or (self.FASTER_JPEG and config['format'] != "MJPEG")) and \
            self.picam2.helpers._get_format_str(file_output, format) in ('jpg', 'jpeg'):
             quality = self.picam2.options.get("quality", 90)
             with MappedArray(self, 'main') as m:

tests/test_list.txt

@@ -95,3 +95,4 @@ tests/allocator_test.py
 tests/allocator_leak_test.py
 tests/wait_cancel_test.py
 tests/stride_test.py
+tests/yuv_capture.py

tests/yuv_capture.py

@@ -0,0 +1,21 @@
+#!/usr/bin/python3
+import time
+
+from picamera2 import Picamera2
+from picamera2.encoders import JpegEncoder
+
+picam2 = Picamera2()
+video_config = picam2.create_video_configuration({"format": "YUV420", "size": (1280, 720)})
+picam2.configure(video_config)
+encoder = JpegEncoder(q=70)
+
+picam2.start_recording(encoder, 'test.mjpeg')
+time.sleep(5)
+picam2.stop_recording()
+
+still_config = picam2.create_still_configuration({"format": "YUV420"})
+picam2.configure(still_config)
+picam2.start()
+
+time.sleep(2)
+picam2.capture_file("test.jpg")