Calculate appropriate texture size.

		Calculate size or required texture so that it will fill the window, 
		but retains the movies original aspect ratio.
		
		Parameters
		----------
		screen_res : tuple
			Display window size/Resolution
		image_res : tuple
		    Image width and height

		Returns
		-------
		tuple 
			width and height of image scaled to window/screen

def calc_scaled_res(self, screen_res, image_res):
		"""Calculate appropriate texture size.

		Calculate size or required texture so that it will fill the window, 
		but retains the movies original aspect ratio.
		
		Parameters
		----------
		screen_res : tuple
			Display window size/Resolution
		image_res : tuple
		    Image width and height

		Returns
		-------
		tuple 
			width and height of image scaled to window/screen
		"""
		rs = screen_res[0]/float(screen_res[1])
		ri = image_res[0]/float(image_res[1])

		if rs > ri:
			return (int(image_res[0] * screen_res[1]/image_res[1]), screen_res[1])
		else:
			return (screen_res[0], int(image_res[1]*screen_res[0]/image_res[0]))