1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
|
% HelloAlphaDemo -- Minimal demonstration of alpha blending.
%
% Derived from code written by Peter Scarfe.
%
PsychDefaultSetup(2);
% Get the screen numbers
screens = Screen('Screens');
% Draw to the external screen if avaliable
screenNumber = max(screens);
% Get value of color white:
white = WhiteIndex(screenNumber)
% Open an on screen window with a white background color:
[window, windowRect] = PsychImaging('OpenWindow', screenNumber, white);
% Set blend function for alpha blending
Screen('BlendFunction', window, GL_SRC_ALPHA, GL_ONE_MINUS_SRC_ALPHA);
% Get the centre coordinate of the window
[xCenter, yCenter] = RectCenter(windowRect);
% Make a base Rect of 300 by 300 pixels
baseRect = [0 0 300 300];
% Screen X positions of our three rectangles:
squareXpos = [xCenter - 200 xCenter + 200 xCenter];
squareYpos = [yCenter yCenter yCenter + 200];
numSqaures = length(squareXpos);
% Set the colors to Red, Green and Blue, with the fourth value being the
% "alpha" value. This also takes a value between 0 and 255 just like a
% normal colour, however now 0 = totally transparent and 255 = totally
% opaque. Our RGB triplets are now RGBA values.
allColors = [1 0 0 1; 0 1 0 1; 0 0 1 0.5]';
% Make our rectangle coordinates
allRects = nan(4, 3);
for i = 1:numSqaures
allRects(:, i) = CenterRectOnPointd(baseRect, squareXpos(i), squareYpos(i));
end
% Draw the rect to the screen
Screen('FillRect', window, allColors, allRects);
% Flip to the screen
Screen('Flip', window);
% Wait for a key press
KbStrokeWait;
% Clear the screen
sca;
|
