HTML5 Canvas API - 用斜体格式化单个单词 [英] HTML5 Canvas API - formatting individual words with italics

问题描述

我在 HTML5 中使用 Canvas API 时遇到了一个小问题.我有一个文本，我必须在 html 页面的画布上显示.

文本示例可以是这是一个斜体字".所以我要做的就是显示我从数据库中获取的文本，但只从句子 Italic 中生成一个单词.所以我必须像这样显示文本:

<块引用>

这是一个斜体字"

所以我的代码是这样的:

var canvas = document.getElementById('myCanvas');var context = canvas.getContext('2d');//文本context.fillStyle = "#000000";context.font = "20px Sans-Serif";context.textBaseline = "top";context.fillText("这是一个", 195, 80 );context.font = 斜体 20px 无衬线字体";context.fillText (斜体", 285, 80 );context.font = "20px Sans-Serif";context.fillText ("text", 330, 80 );

所以这段代码实际上并不是动态的，我一直都知道从哪里开始句子其余部分的正确像素.有没有人知道如何动态和干净地解决这个问题?

解决方案

为了获得某种灵活性，您必须在文本中确定一个约定，以表明样式已更改.
而且，您必须使用 measureText 来填充文本的单独运行"，每次运行都使用正确的样式，measureText(thisRun).width 将为您提供以像素为单位的大小当前运行的.
然后你需要的是绘制单独的文本运行，每个文本都有自己的风格，然后根据 measureText 的返回值在光标"上移动.

举个简单的例子，我把§r"=常规文本，§i"=斜体，§b"=粗体，§l"=更轻，字符串作为样式约定:

var text = "这是一个 §iItalic§r、一个 §bbold§r 和一个 §llighter§r 文本";

将输出为:

小提琴在这里:

http://jsfiddle.net/gamealchemist/32QXk/6/

代码是:

var canvas = document.getElementById('myCanvas');var context = canvas.getContext('2d');//文本中用于提及样式更改的标记var styleMarker = '§';//表格代码样式 -->字体样式var styleCodeToStyle = {r: '',我:'斜体'，b: '大胆',l:'更轻'};//示例文本var text = "这是一个 §iItalic§r、一个 §bbold§r 和一个 §llighter§r 文本";//示例绘制drawStyledText(text, 20, 20, 'Sans-Serif', 20);//示例文本 2 :var text2 = "这是一个具有单独样式数据的文本";var 粗体字 = [ 3, 5, 8 ];var italicWords = [ 2, 4 , 7];var words = text2.split(" ");var newText ='';for (var i=0; i

I have a small problem using Canvas API in HTML5. I have a text that I have to show on a canvas in an html page.

The text example can be "This is an Italic word". So what I have to do is display this text that I take from the database, but to make just one word from the sentence Italic. So I have to display the text like this:

"This is an Italic word"

So my code looks like this:

var canvas = document.getElementById('myCanvas');
var context = canvas.getContext('2d');

//text
context.fillStyle  = "#000000";
context.font = "20px Sans-Serif";
context.textBaseline = "top";
context.fillText  ("This is an ", 195, 80 );

context.font = "italic 20px Sans-Serif";
context.fillText  ("Italic", 285, 80 );
context.font = "20px Sans-Serif";
context.fillText  ("text", 330, 80 );

So this code is not actually dynamic and I have all the time to know the correct pixel where to start the rest of the sentence. Does anybody have an idea how can I solve this issue dynamically and clean ?

解决方案

To achieve some kind of flexibility, you have to decide of a convention inside your text that will tell that the style changed.
And also, you'll have to use measureText to be able to fillText separate 'runs' of the text, each run using the right style, measureText(thisRun).width will give you the size in pixels of the current run.
Then what you need is to draw separate text runs, each in its own style, then move on the 'cursor' based on the return value of measureText.

For a quick example, i took as styling convention "§r" = regular text, "§i" = italic, "§b" = bold, "§l" = lighter, so the string :

var text = "This is an §iItalic§r, a §bbold§r, and a §llighter§r text";

will output as :

fiddle is here :

http://jsfiddle.net/gamealchemist/32QXk/6/

The code is :

var canvas = document.getElementById('myCanvas');
var context = canvas.getContext('2d');

// marker used in the text to mention style change
var styleMarker = '§';

// table code style --> font style
var styleCodeToStyle = {
    r: '',
    i: 'italic',
    b: 'bold',
    l: 'lighter'
};

// example text
var text = "This is an §iItalic§r, a §bbold§r, and a §llighter§r text";

// example draw
drawStyledText(text, 20, 20, 'Sans-Serif', 20);

// example text 2 : 

var text2 = "This is a text that has separate styling data";
var boldedWords = [ 3, 5, 8 ];
var italicWords = [ 2, 4 , 7];

var words = text2.split(" ");
var newText ='';

for (var i=0; i<words.length; i++) {
  var thisWord = words[i];
  if (boldedWords.indexOf(i)!=-1) 
      newText += '§b' + thisWord + '§r ';
   else if (italicWords.indexOf(i)!=-1) 
      newText += '§i' + thisWord + '§r ';
    else 
       newText += thisWord + ' ';
}

drawStyledText(newText, 20, 60, 'Sans-Serif', 20);


function drawStyledText(text, x, y, font, fontSize) {
    // start with regular style
    var fontCodeStyle = 'r';
    do {
        // set context font
        context.font = buildFont(font, fontSize, fontCodeStyle);
        // find longest run of text for current style
        var ind = text.indexOf(styleMarker);
        // take all text if no more marker
        if (ind == -1) ind = text.length;
        // fillText current run
        var run = text.substring(0, ind);
        context.fillText(run, x, y);
        // return if ended
        if (ind == text.length) return;
        // move forward
        x += context.measureText(run).width;
        // update current style
        fontCodeStyle = text[ind + 1];
        // keep only remaining part of text
        text = text.substring(ind + 2);
    } while (text.length > 0)
}


function buildFont(font, fontSize, fontCodeStyle) {
    var style = styleCodeToStyle[fontCodeStyle];
    return style + ' ' + fontSize + 'px' + ' ' + font;
}

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