Merge pull request #485 from jcozar87/doc-picamera-zoom

doc: Slightly zoom property documentation improvement

docs/fov.rst

@@ -527,8 +527,9 @@ recorded. The components that data passes through are as follows:
 
     - **Resizing**: At this point, the frame is resized to the requested output
       resolution (all prior stages have been performed on "full" frame data
-      at whatever resolution the sensor is configured to produce). See
-      :attr:`~PiCamera.resolution`.
+      at whatever resolution the sensor is configured to produce). Firstly, the
+      zoom is applied (see :attr:`~PiCamera.zoom`) and then the image is resized
+      to the requested resolution (see :attr:`~PiCamera.resolution`).
 
    Some of these steps can be controlled directly (e.g. brightness, noise
    reduction), others can only be influenced (e.g. analog and digital gain),

picamera/camera.py

@@ -3422,6 +3422,11 @@ def _set_zoom(self, value):
         the "Region of Interest" or ROI). The default value is ``(0.0, 0.0,
         1.0, 1.0)`` which indicates that everything should be included. The
         property can be set while recordings or previews are in progress.
+
+        The `zoom` is applied to the processed image, after rotation and rescale.
+        If rotation has been used, zoom is composed of ``(y, x, h, w)`` instead.
+        The values `w` and `h` can modify the aspect ratio of the image: use equal
+        values for `w` and `h` if you want to keep the same the aspect ratio. 
         """)
 
     def _get_crop(self):