Mention the 'frame' argument to the vision API

Based on a previous patch which Dan put together, updated and
with some fixes applied.

Co-Authored-By: Dan Trickey <[email protected]>

Author: PeterJCLaw

programming/sr/cheat_sheet.md

@@ -191,6 +191,22 @@ for marker in markers:
     marker.orientation.rotation_matrix
 ~~~~~
 
+## Getting the frame from the camera
+
+It is also possible to get an OpenCV frame from the camera:
+
+~~~~~ python
+frame = R.camera.capture()
+~~~~~
+
+You can use this frame in your own vision processing, or use it with other vision commands.
+
+~~~~~ python
+markers = R.camera.see(frame=frame)
+marker_ids = R.camera.see_ids(frame=frame)
+R.camera.save('photo.jpg', frame=frame)
+~~~~~
+
 ## Ruggeduino
 
 ### Setting the mode of a pin

programming/sr/vision/index.md

@@ -85,6 +85,14 @@ frame = R.camera.capture()
 flipped = cv2.flip(frame, 0)
 ~~~~~
 
+You can also use a frame with other vision commands to avoid recapturing. This may be useful if you wish to use both your own vision algorithms and our vision on the same frames.
+
+~~~~~ python
+markers = R.camera.see(frame=frame)
+marker_ids = R.camera.see_ids(frame=frame)
+R.camera.save('photo.jpg', frame=frame)
+~~~~~
+
 [Field of View](#fov) {#fov}
 -------------------