PTBtutorials—TextDemos

% Draw text in the upper portion of the screen with the default font in red
Screen(‘TextSize‘, window, 70);
DrawFormattedText(window, ‘Hello World‘, ‘center‘,...
    screenYpixels * 0.25, [1 0 0]);

% Draw text in the middle of the screen in Courier in white
Screen(‘TextSize‘, window, 80);
Screen(‘TextFont‘, window, ‘Courier‘);
DrawFormattedText(window, ‘Hello World‘, ‘center‘, ‘center‘, white);

% Draw text in the bottom of the screen in Times in blue
Screen(‘TextSize‘, window, 90);
Screen(‘TextFont‘, window, ‘Times‘);
DrawFormattedText(window, ‘Hello World‘, ‘center‘,...
    screenYpixels * 0.75, [0 0 1]);

% Lets write three lines of text, the first and second right after one          第一行与第二行紧挨着，但是第三行与这两行之间空了一行。这里使用了
% another, and the third with a line space in between. To add line spaces   特殊符号"\n",是换行符
% we use the special characters "\n"
line1 = ‘Hello World‘;
line2 = ‘\n This is the second line‘;
line3 = ‘\n\n This is the third line‘;

% Draw all the text in one go            一次性绘制文本
Screen(‘TextSize‘, window, 70);
DrawFormattedText(window, [line1 line2 line3],...
    ‘center‘, screenYpixels * 0.25, white);

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

% Draw text in the upper portion of the screen with the default font in red          最上一行，默认字体，红色，水平翻转
% and flipped horizontally
Screen(‘TextSize‘, window, 70);
DrawFormattedText(window, ‘Hello World‘, ‘center‘,...
    screenYpixels * 0.25, [1 0 0], [], 1);

% Draw text in the middle of the screen in Courier in white and flipped              中间行，Courier字体，白色，垂直翻转
% vertically
Screen(‘TextSize‘, window, 80);
Screen(‘TextFont‘, window, ‘Courier‘);
DrawFormattedText(window, ‘Hello World‘, ‘center‘, ‘center‘, white, [], [], 1);      最底行，Times字体，蓝色，水平和垂直翻转

% Draw text in the bottom of the screen in Times in blue and flipped
% horizontally and vertically i.e. upside down
Screen(‘TextSize‘, window, 90);
Screen(‘TextFont‘, window, ‘Times‘);
DrawFormattedText(window, ‘Hello World‘, ‘center‘,...
    screenYpixels * 0.75, [0 0 1], [], 1, 1);

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

% Get the nominal framerate of the monitor. For this simple timer we are    获取显示器的刷新率，60hz
% going to change the counterdown number every second. This means we
% present each number for "frameRate" amount of frames. This is because
% "framerate" amount of frames is equal to one second. Note: this is only
% for a very simple timer to demonstarte the principle. You can make more
% accurate sub-second timers based on this.
nominalFrameRate = Screen(‘NominalFrameRate‘, window);

% Our timer is going to start at 10 and count down to 0. Here we make a         获取显示数字的数组，共601个数字
% list of the number we are going to present on each frame. This way of
% doing things is just for you to see what is going on more easily. You
% could eliminate this step completely by simply keeping track of the time
% and updating the clock appropriately, or by clever use of the Screen Flip command
% However, for this simple demo, this should work fine
presSecs = [sort(repmat(1:10, 1, nominalFrameRate), ‘descend‘) 0];

% We change the color of the number every "nominalFrameRate" frames   改变每一帧数的颜色
colorChangeCounter = 0;

% Randomise a start color  随机生成颜色
color = rand(1, 3);

% Here is our drawing loop
for i = 1:length(presSecs)

    % Convert our current number to display into a string     将数字转换为字符
    numberString = num2str(presSecs(i));

    % Draw our number to the screen            绘制文本
    DrawFormattedText(window, numberString, ‘center‘, ‘center‘, color);

    % Flip to the screen
    Screen(‘Flip‘, window);
 
    % Decide if to change the color on the next frame          确定下一帧是否需要改变颜色
    colorChangeCounter = colorChangeCounter + 1;          
    if colorChangeCounter == nominalFrameRate
        color = rand(1, 3);
        colorChangeCounter = 0;
    end

end

% Our text will oscilate with a sine wave function to the left and right   文本会随着正弦函数在屏幕上左右移动
% of the screen. These are the parameters for the sine wave
% See: http://en.wikipedia.org/wiki/Sine_wave        正弦函数的参数
amplitude = screenXpixels * 0.2;                     振幅
frequency = 0.2;                                     频率
angFreq = 2 * pi * frequency;                        角频率，单位是弧度/秒
time = 0;                                            时间

% Our two text strings will be pi out of phase        这两个字符串是反相的
startPhaseOne = 0;
startPhaseTwo = pi;

% Sync us and get a time stamp
vbl = Screen(‘Flip‘, window);
waitframes = 1;

% Maximum priority level
topPriorityLevel = MaxPriority(window);
Priority(topPriorityLevel);

% Loop the animation until a key is pressed
while ~KbCheck

    % Position of the two text strings on this frame            某一帧上字符串的位置
    xposOne = amplitude * sin(angFreq * time + startPhaseOne);     
    xposTwo = amplitude * sin(angFreq * time + startPhaseTwo);

    % Add this position to the screen center coordinate.         将这个位置添加到屏幕中心坐标
    squareXposOne = xCenter + xposOne;
    squareXposTwo = xCenter + xposTwo;

    % Draw the text to the screen                                将文本绘制到屏幕上
    DrawFormattedText(window, ‘Hello World‘, squareXposOne,...
        screenYpixels * 0.25, [1 0 0]);
    DrawFormattedText(window, ‘Hello World‘, squareXposTwo,...
        screenYpixels * 0.75, [1 0 1]);

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

    % Increment the time                                        时间增量
    time = time + ifi;

end

% Draw text in the middle of the screen. We just to this so that we can get 
% the text bounds. These are the "dimensions" of the text as it would be             将文本绘制到屏幕上，以获得文本边界
% drawn to the screen                                                        返回值textBounds疑似包括的是文本所在边界的左上与右下坐标
Screen(‘TextSize‘, window, 80);
[~, ~, textBounds] = DrawFormattedText(window, ‘Hello World‘, ‘center‘, ‘center‘, white);      

% Over-write the screen in grey so that it is back to its original state                将屏幕重新变为灰色
Screen(‘FillRect‘, window, grey);

% Make a rectangular texture to hold our text. This has the same background
% color to that of the screen. Note also, that we increase the size of the
% text bounds slightly and round upwards to the nearest pixel. This is to
% make sure the text fits in the texture and because texture dimensions can
% only be to interger pixels.
textureRect = ones(ceil((textBounds(4) - textBounds(2)) * 1.1),...                          制作纹理来包含文本，得到的是一个近似相同大小的灰色纹理区
    ceil((textBounds(3) - textBounds(1)) * 1.1)) .* grey;
textTexture = Screen(‘MakeTexture‘, window, textureRect);

% Set the text size for this texture and then draw our text to the texture,              设置纹理的字体大小，然后将文本绘制到该纹理上，就如同绘制在屏幕上
% just as if we were drawing it to the screen
Screen(‘TextSize‘, textTexture, 80);                                                          

% No draw our text, but here we draw it to a texture "pretending" that it is              绘制文本到纹理上，假装纹理是屏幕
% the screen
DrawFormattedText(textTexture, ‘Hello World‘, ‘center‘, ‘center‘, white);

% Sync us and get a time stamp                                                           获取时间戳
vbl = Screen(‘Flip‘, window);
waitframes = 1;

% Maximum priority level
topPriorityLevel = MaxPriority(window);
Priority(topPriorityLevel);

% Angular increment per frame, one rotation every 2 seconds                             获取每一帧角度的增加值，这里每2s旋转360度
% (just an arbitary nice value)
anglePerFrame = 360 * ifi / 2;
currentAngle = 0;

% Animation loop
while ~KbCheck

    % Here we draw our texture to the screen. This texture contains our                   将纹理绘制到屏幕上，这个纹理包含我们预先绘制好的文本并
    % predrawn text and allows us to rotate it easily.                                 允许我们对其进行旋转
    Screen(‘DrawTextures‘, window, textTexture, [], [], currentAngle);

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

    % Increment the angle
    currentAngle = currentAngle + anglePerFrame;

end