ppd_from_length_visual_angle
============================



.. py:function:: stimupy.utils.ppd_from_length_visual_angle(length, visual_angle)


   Calculate pixels-per-degree from length (pixels) and visual angle (degrees)

   :param length: length in pixels
   :type length: int or None
   :param visual_angle: visual angle in degrees
   :type visual_angle: float or None

   :rtype: visual angle (degrees) translated to length (pixels)