grabcut.py sample: Allow drawing rect from bottom/right

The grabcut sample script isn't able to create rectangles correctly that are
drawn from e.g. bottom-right to top-left.
This small commit uses four min() calls to determine the correct
top-left point of the rectangle.
It also removes some unnecessary white spaces before colons.

samples/python2/grabcut.py

@@ -63,14 +63,14 @@ def onmouse(event,x,y,flags,param):
         if rectangle == True:
             img = img2.copy()
             cv2.rectangle(img,(ix,iy),(x,y),BLUE,2)
-            rect = (ix,iy,abs(ix-x),abs(iy-y))
+            rect = (min(ix,x),min(iy,y),abs(ix-x),abs(iy-y))
             rect_or_mask = 0
 
     elif event == cv2.EVENT_RBUTTONUP:
         rectangle = False
         rect_over = True
         cv2.rectangle(img,(ix,iy),(x,y),BLUE,2)
-        rect = (ix,iy,abs(ix-x),abs(iy-y))
+        rect = (min(ix,x),min(iy,y),abs(ix-x),abs(iy-y))
         rect_or_mask = 0
         print " Now press the key 'n' a few times until no further change \n"