PROPixx Demo 4 -- Drawing dots at 1440 Hz with automatic quadrant assignment
===============================================================================

This demo is a simple demonstration of the PROPixx's 1440 Hz sequencer. We display a white dot rotating in a circle around the middle of the display, refreshing at 1440 Hz. This demo uses Psychtoolbox's ``PsychProPixx`` functions to automate quadrant and color channel assignment. 

To display images at 1440 Hz, the PROPixx uses a sequencer to break up a 1920 x 1080 120 Hz RGB video signal into 12 individual frames. The 1920 x 1080 image is first divided into quadrants, which are magnified to full screen. Each 8-bit RGB color channel is then converted to grayscale. The order of frame presentation is: Q1 red, Q2 red, Q3 red, Q4 red, Q1 green, Q2 green, Q3 green, Q4 green, Q1 blue, Q2 blue, Q3 blue, Q4 blue. Below is a visual representation of this process:

.. image:: Quad12xStill.*
  :width: 500
  :align: center

In our previous DrawDots demos, we manually assigned our stimuli to the correct quadrant and color channel of the 1920 x 1080 display, so that the stimuli appeared in the correct order on the 1440 Hz display. ``PsychProPixx`` automates this process. To generate our stimuli we simply do the following:

1. Create an offscreen 960 x 540 image with ``PsychProPixx('GetImageBuffer')`` 
2. Draw our frame contents to this image 
3. Add the image to a queue using ``PsychProPixx('QueueImage')``
4. When 12 frames have been added to the queue, PsychProPixx constructs a 1920 x 1080 RGB image and flips it to the display. The sequencer then displays the frames one after the other.


.. literalinclude:: ../DatapixxToolbox/DatapixxDemos/PPxDraw1440HzDots3.m
   :language: matlab
   :emphasize-lines: 63-64, 92-99, 121
   :linenos: