added scale_up and scale_down function to Actor to resize images

doc/builtins.rst

@@ -591,6 +591,24 @@ Remember that angles loop round, so 0 degrees == 360 degrees == 720 degrees.
 Likewise -180 degrees == 180 degrees.
 
 
+Scaling
+'''''''
+.. versionadded:: 1.3
+
+To resize and Actor, use ``scale_up`` and ``scale_down``. These will change the
+dimensions of the Actor by a given factor. For example, ``scale_up(2)``
+will increase Actor's width and height 2x.::
+
+    alien = Actor('alien')
+    alien.scale_up(2)
+
+    def draw():
+        alien.draw()
+
+Scaling the Actor does not change the file size of the image. Significantly
+scaling images with large file sizes will not reduce the memory taken by the
+images.::
+
 Distance and angle to
 '''''''''''''''''''''
 

pgzero/actor.py

@@ -353,5 +353,18 @@ def distance_to(self, target):
         dy = ty - myy
         return sqrt(dx * dx + dy * dy)
 
+    def scale_up(self, value):
+        """Scales up the image by a factor of the inputted value."""
+        self._orig_surf = pygame.transform.scale(self._surf, (int(self._surf.get_width() * value), int(self._surf.get_height() * value)))
+        self._surf = self._orig_surf
+        self._update_pos()
+
+    def scale_down(self, value):
+        """Scales down the image by a factor of the inputted value."""
+        self._orig_surf = pygame.transform.scale(self._surf, (self._surf.get_width() // value, self._surf.get_height() // value))
+        self._surf = self._orig_surf
+        self._update_pos()
+
+
     def unload_image(self):
         loaders.images.unload(self._image_name)