% Clear the workspace and the screen
close all;

% Here we call some default settings for setting up Psychtoolbox

% Get the screen numbers. This gives us a number for each of the screens
% attached to our computer.
screens = Screen('Screens');

% To draw we select the maximum of these numbers. So in a situation where we
% have two screens attached to our monitor we will draw to the external
% screen.
screenNumber = max(screens);

% Define black and white (white will be 1 and black 0). This is because
% in general luminace values are defined between 0 and 1 with 255 steps in
% between. With our setup, values defined between 0 and 1.
white = WhiteIndex(screenNumber);
black = BlackIndex(screenNumber);

% Do a simply calculation to calculate the luminance value for grey. This
% will be half the luminace value for white
grey = white / 2;

% Open an on screen window using PsychImaging and color it grey.
[window, windowRect] = PsychImaging('OpenWindow', screenNumber, grey);

% Now we have drawn to the screen we wait for a keyboard button press (any
% key) to terminate the demo.

% Clear the screen.