minimal.m

Screen('Preference', 'SkipSyncTests', 2)

PsychDefaultSetup(2);

screenId = max(Screen('Screens')); % get screen ID

PsychImaging('PrepareConfiguration');
PsychImaging('AddTask', 'General', 'UseFastOffscreenWindows');
PsychImaging('AddTask', 'General', 'FloatingPoint32Bit');

window = PsychImaging('OpenWindow',screenId,0.5); % open screen with background luminance 0.5

%Screen('BlendFunction', window, 'GL_ONE', 'GL_ZERO');

tex = Screen('MakeTexture',window,0.5); % create a texture with luminance 0.5

rect = [0,0,500,500]; % define texture rect as upper left 500x500 pixels of screen

for x = 1:20

	if mod(x,2)
		Screen('FrameRect', window, [1 1 1], [501 501 506 506]);

		Screen('Flip',window); % flip
	else
		Screen('FrameRect', window, [1 1 0], [501 501 506 506]);

		Screen('DrawTexture',window,tex,[],rect); % draw

		Screen('Flip',window); % flip	
	end
	
	WaitSecs(1);
	
end

sca %close screen