···

       
16
       
16
       
 
       
        self.width = width

     

       
17
       
17
       
 
       
        self.height = height

     

       
18
       
18
       
 
       
        if origin == 'center':

     

       
19
       
19
       
-
       
            self.viewBox = (width/2, height/2, width, height)

     

       
19
       
19
       
+
       
            self.viewBox = (-width/2, -height/2, width, height)

     

       
20
       
20
       
 
       
        else:

     

       
21
       
21
       
 
       
            origin = tuple(origin)

     

       
22
       
22
       
 
       
            assert len(origin) == 2