[bebop] video: more variables to configure and some comments (#1818)

Added an example in the comments about what you can and can't do with the camera (as far as I explored up till now).

sw/airborne/boards/bebop.h

@@ -36,6 +36,32 @@
 #define MT9F002_OUTPUT_WIDTH 2048
 #endif
 
+#ifndef MT9F002_INITIAL_OFFSET_X
+#define MT9F002_INITIAL_OFFSET_X 1000 // pixels in the raw sensor!!
+#endif
+
+#ifndef MT9F002_INITIAL_OFFSET_Y
+#define MT9F002_INITIAL_OFFSET_Y 0 // pixels in the raw sensor!!
+#endif
+
+/** Our output is only OUTPUT_SCALER of the pixels we take of the sensor
+ * 	Example:
+ * 	output_width = 512
+ * 	output_height = 830
+ * 	output_scaler = 0.25
+ * 	We now get an image of 512 by 830 which contains a "compressed version"
+ * 	of what would normally be an image of 2048 by 3320.
+ * 	Be warned: set your offset x appropriately.
+ * 	Example of what could go wrong:
+ * 	output_width = 512
+ * 	output_height = 830
+ * 	output_scaler = 0.25
+ * 	offset_x = 1500
+ * 	We now ask for pixels outside the 4608H x 2592V sensor or the 3320H x 2048W of the ISP.
+ */
+#ifndef MT9F002_OUTPUT_SCALER
+#define MT9F002_OUTPUT_SCALER 1.0
+#endif
 /** uart connected to GPS internally */
 #define UART1_DEV /dev/ttyPA1
 

sw/airborne/boards/bebop/board.c

@@ -123,9 +123,9 @@ void board_init2(void)
     .gain_green2 = 2.0,
     .output_width = MT9F002_OUTPUT_WIDTH,
     .output_height = MT9F002_OUTPUT_HEIGHT,
-    .output_scaler = 1.0,
-    .offset_x = 1000,
-    .offset_y = 0,
+    .output_scaler = MT9F002_OUTPUT_SCALER,
+    .offset_x = MT9F002_INITIAL_OFFSET_X,
+    .offset_y = MT9F002_INITIAL_OFFSET_Y,
 
     // I2C connection port
     .i2c_periph = &i2c0