checkerboard_21
===============


.. image:: /_static/generated_stimuli/papers.RHS2007.checkerboard_21.png
   :alt: checkerboard_21 stimulus example
   :align: center
   :width: 400px






.. py:function:: stimupy.papers.RHS2007.checkerboard_21(ppd=PPD, pad=True)


   Checkerboard stimulus as shown in Robinson, Hammon, & de Sa (2007) Fig 1w.
   Stimulus size: 6.28125x20.9375 deg
   Target size: 2.09x2.09 deg

   :param ppd: Resolution of stimulus in pixels per degree. (default: 32)
   :type ppd: int
   :param pad: If True, include padding to 32x32 deg (default: True)
   :type pad: bool

   :returns: dict with the stimulus (key: "img") and target mask (key: "target_mask")
             and additional keys containing stimulus parameters
   :rtype: dict of str

   .. rubric:: References

   Blakeslee, B., & McCourt, M. E. (2004).
       A unified theory of brightness contrast and assimilation
       incorporating oriented multi-scale spatial filtering and contrast normalization.
       Vision Research, 44, 2483-2503.
   DeValois, R. L., & DeValois, K. K. (1988).
       Spatial vision.
       New York: Oxford University Press.