PTBtutorials—The basics

% Clear the workspace and the screen   清除工作空间和多余窗口
sca;
close all;
clearvars;

% Here we call some default settings for setting up Psychtoolbox   调用默认设置
PsychDefaultSetup(2);

% Get the screen numbers. This gives us a number for each of the screens  获取屏幕数量
% attached to our computer.
screens = Screen(‘Screens‘);

% To draw we select the maximum of these numbers. So in a situation where we  选择最大值
% 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   定义黑色和白色
% between. All values in Psychtoolbox are defined between 0 and 1
white = WhiteIndex(screenNumber);
black = BlackIndex(screenNumber);

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

% Open an on screen window using PsychImaging and color it grey.   打开窗口.也可以将PsychImaging替换为Screens
[window, windowRect] = PsychImaging(‘OpenWindow‘, screenNumber, grey);

% Now we have drawn to the screen we wait for a keyboard button press (any   按任意键结束demo
% key) to terminate the demo.
KbStrokeWait;

% Clear the screen.  关闭屏幕
sca;

% Measure the vertical refresh rate of the monitor
ifi = Screen(‘GetFlipInterval‘, window);

% Retreive the maximum priority number  检索最大优先级
topPriorityLevel = MaxPriority(window);

% Length of time and number of frames we will use for each drawing test
numSecs = 1;
numFrames = round(numSecs / ifi);

% Numer of frames to wait when specifying good timing. Note: the use of
% wait frames is to show a generalisable coding. For example, by using
% waitframes = 2 one would flip on every other frame. See the PTB
% documentation for details. In what follows we flip every frame.
waitframes = 1;

%------------
% EXAMPLE #1
%------------

% First we will demonstrate a poor way in which to get good timing of
% visually presented stimuli. We generally use this way of presenting in    在硬件有缺陷时采用这样的程序，一般并不推荐这种
% the demos in order to allow the demos to run on potentially defective
% hardware. In this way of presenting we leave much to chance as regards
% when our stimuli get to the screen, so it is not reccomended that you use
% this approach.
for frame = 1:numFrames

    % Color the screen grey
    Screen(‘FillRect‘, window, [0.5 0.5 0.5]);

    % Flip to the screen
    Screen(‘Flip‘, window);

end
%------------
% EXAMPLE #2
%------------

% Finally we do the same as the last example except now we additionally
% tell PTB that no more drawing commands will be given between coloring the
% screen and the flip command. This, can help acheive good timing when one
% is needing to do additional non-PTB processing between setting up drawing
% and flipping to the screen. Thus, you would only use this technique if
% you were doing this. So, if you are not, go with example #3
Priority(topPriorityLevel); 将PTB优先级设置为最高，使其先于其他系统和应用程序。建议在设置窗口后，脚本开始时立刻设置优先级
vbl = Screen(‘Flip‘, window); 获取刷屏完成的时刻
for frame = 1:numFrames

    % Color the screen blue
    Screen(‘FillRect‘, window, [0 0 0.5]);

    % Tell PTB no more drawing commands will be issued until the next flip  告知PTB在翻转页面前没有进一步绘制的要求，使得PTB对绘制操作进行优化处理。
    Screen(‘DrawingFinished‘, window);                                         但是不要在一次页面切换前多次使用该命令，否则会影响性能
                                                                                 如果需要在绘制与翻转间需要其他非PTB操作，可以这样。不需要则可以省略该步骤
% Flip to the screen
    vbl = Screen(‘Flip‘, window, vbl + (waitframes - 0.5) * ifi); 这里使用了一半的刷屏周期（半帧），确保PTB实现我们所想要的时程

end
Priority(0);

% Measure the vertical refresh rate of the monitor
ifi = Screen(‘GetFlipInterval‘, window);

% Retreive the maximum priority number and set max priority
topPriorityLevel = MaxPriority(window);
Priority(topPriorityLevel);

% Here we use to a waitframes number greater then 1 to flip at a rate not
% equal to the monitors refreash rate. For this example, once per second,
% to the nearest frame
flipSecs = 1;
waitframes = round(flipSecs / ifi);    和上面的示例3基本一致，只是图像更新的速率变为了1s一次

% Flip outside of the loop to get a time stamp
vbl = Screen(‘Flip‘, window);

% Run until a key is pressed
while ~KbCheck

    % Color the screen a random color
    Screen(‘FillRect‘, window, rand(1, 3));

    % Flip to the screen
    vbl = Screen(‘Flip‘, window, vbl + (waitframes - 0.5) * ifi);

end

% Open an on screen window 打开窗口
[window, windowRect] = PsychImaging(‘OpenWindow‘, screenNumber, black);

% Get the size of the on screen window   获取显示器像素大小
[screenXpixels, screenYpixels] = Screen(‘WindowSize‘, window);

% Query the frame duration  获取刷屏周期
ifi = Screen(‘GetFlipInterval‘, window);

% Setup the text type for the window  设置字体与字号
Screen(‘TextFont‘, window, ‘Ariel‘);
Screen(‘TextSize‘, window, 50);

% Get the centre coordinate of the window 获取屏幕中心位置的坐标
[xCenter, yCenter] = RectCenter(windowRect);

% Here we set the initial position of the mouse to a random position on the  将鼠标的初始位置设置为随机值
% screen
SetMouse(round(rand * screenXpixels), round(rand * screenYpixels), window);

% Set the mouse to the top left of the screen to start with 设置到屏幕左上角
SetMouse(0, 0, window);

% Loop the animation until a key is pressed  
while ~KbCheck   检测按键。若没有按键，则该循环一直进行

    % Get the current position of the mouse
    [x, y, buttons] = GetMouse(window);  获取鼠标位置与按键状况

    % We clamp the values at the maximum values of the screen in X and Y 如果连接了两台显示器，将坐标值限制在屏幕最大值内
    % incase people have two monitors connected. This is all we want to
    % show for this basic demo.
    x = min(x, screenXpixels);
    y = min(y, screenYpixels);

    % Construct our text string
    textString = [‘Mouse at X pixel ‘ num2str(round(x))...
        ‘ and Y pixel ‘ num2str(round(y))];

    % Text output of mouse position draw in the centre of the screen
    DrawFormattedText(window, textString, ‘center‘, ‘center‘, white); 绘制文本

    % Draw a white dot where the mouse cursor is
    Screen(‘DrawDots‘, window, [x y], 10, white, [], 2);  在鼠标所在位置处画点

    % Flip to the screen
    Screen(‘Flip‘, window);

end