extend demo to switch camera and add documentation

Author: brean

README.md

@@ -30,7 +30,7 @@ At present this is in the format of a numpy array with dimensions (width, height
 The drone's property `navdata` contains always the latest navdata.
 You can for example get the current battery charge from that:
 
-```
+```python
 >>> bat = drone.navdata.get(0, dict()).get('battery', 0)
 >>> print('Battery: %i%%' % bat)
 ```
@@ -43,12 +43,17 @@ and lets you remote-control the drone with the keyboard (you need pygame for it
 
     RETURN      - takeoff
     SPACE       - land
-    BACKSPACE   - reset (from emergency)
-    a/d         - left/right
-    w/s         - forward/back
+    BACKSPACE   - reset (from emergency - DO NOT USE IN FLIGHT)
+    w           - forward
+    a           - left
+    s           - back
+    d           - right
+    LEFT/q      - turn left
+    RIGHT/e     - turn right
     1,2,...,0   - speed
     UP/DOWN     - altitude
-    LEFT/RIGHT  - turn left/right
+    r           - switch to front facing camera
+    f           - switch to downward facing camera
 
 Here is a [video] of the library in action:
 

demo/demo_pygame.py

@@ -54,10 +54,8 @@ def main():
                     running = False
                 # takeoff / land
                 elif event.key == pygame.K_RETURN:
-                    print("return")
                     drone.takeoff()
                 elif event.key == pygame.K_SPACE:
-                    print("space")
                     drone.land()
                 # emergency
                 elif event.key == pygame.K_BACKSPACE:
@@ -78,9 +76,9 @@ def main():
                 elif event.key == pygame.K_DOWN:
                     drone.move_down()
                 # turn left / turn right
-                elif event.key == pygame.K_LEFT:
+                elif event.key in [pygame.K_LEFT, pygame.K_q]:
                     drone.turn_left()
-                elif event.key == pygame.K_RIGHT:
+                elif event.key in [pygame.K_RIGHT, pygame.K_e]:
                     drone.turn_right()
                 # speed
                 elif event.key == pygame.K_1:
@@ -103,11 +101,13 @@ def main():
                     drone.speed = 0.9
                 elif event.key == pygame.K_0:
                     drone.speed = 1.0
-
+                elif event.key == pygame.K_r:
+                    drone.set_camera_view(True)
+                elif event.key == pygame.K_f:
+                    drone.set_camera_view(False)
         try:
-            # print pygame.image
             pixelarray = drone.get_image()
-            if pixelarray != None:
+            if (not pixelarray is None) and pixelarray.any():
                 surface = pygame.surfarray.make_surface(pixelarray)
                 rotsurface = pygame.transform.rotate(surface, 270)
                 screen.blit(rotsurface, (0, 0))
@@ -117,6 +117,8 @@ def main():
             f = pygame.font.Font(None, 20)
             hud = f.render('Battery: %i%%' % bat, True, hud_color)
             screen.blit(hud, (10, 10))
+        except KeyboardInterrupt:
+            break
         except:
             pass