我正在尝试将mathML渲染到HTML5画布中。到目前为止,最好的suggestion是将mathML作为SVG异物嵌入,渲染为图像,然后将图像渲染为画布。

问题在于,这种方法在Firefox中有效,但在iPad上失败。您可以在此处看到一些示例:


  渲染mathML as SVG。适用于Firefox和iPad。
  渲染mathML in the canvas。适用于FF。在iPad上失败。
  一个debug version of canvas rendering。绘图被延迟到mouseDown为止。这允许在iPad上使用firebug lite


canvas.html示例中的代码是:

<!DOCTYPE html>
<html lang="en">
  <head>
<meta http-equiv="Content-Type" content="text/html;charset=utf-8" >
        <title>Canvas Test</title>
<script type="text/javascript" src="http://ajax.googleapis.com/ajax/libs/jquery/1.7.1/jquery.min.js"></script>
<script src="http://code.jquery.com/mobile/1.0.1/jquery.mobile-1.0.1.js"></script>
    <script type="text/javascript">

window.addEventListener('load', function () {
    var drawMath = function() {
    // Get the canvas element.
    var elem = document.getElementById('myCanvas');
    var ctx = elem.getContext("2d");
    var data = "<svg xmlns='http://www.w3.org/2000/svg' width='200' height='200'>" +
            "<foreignObject width='100%' height='100%'>" +
            "<div xmlns='http://www.w3.org/1999/xhtml' style='font-size:20px'>" +
        "<math xmlns='http://www.w3.org/1998/Math/MathML' display='block'>" +
        "<mrow>" +
        "<mi _moz-math-font-style='italic'>x</mi>" +
        "<mo>=</mo>" +
        "<mfrac>" +
        "<mrow>" +
        "<mo>&#x2212;</mo>" +
        "<mi _moz-math-font-style='italic'>b</mi>" +
        "<mo>&#xB1;</mo>" +
        "<msqrt>" +
        "<mrow>" +
        "<msup>" +
        "<mi _moz-math-font-style='italic'>b</mi>" +
        "<mn>2</mn>" +
        "</msup>" +
        "<mo>&#x2212;</mo>" +
        "<mn>4</mn>" +
        "<mi _moz-math-font-style='italic'>a</mi>" +
        "<mi _moz-math-font-style='italic'>c</mi>" +
        "</mrow>" +
        "</msqrt>" +
        "</mrow>" +
        "<mrow>" +
        "<mn>2</mn>" +
        "<mi _moz-math-font-style='italic'>a</mi>" +
        "</mrow>" +
        "</mfrac>" +
        "</mrow>" +
        "</math>" +
            "</div>" +
            "</foreignObject>" +
            "</svg>";
    var DOMURL = self.URL || self.webkitURL || self;
    mathimg = new Image();
    var svg = new Blob([data], {type: "image/svg+xml;charset=utf-8"});
    var url = DOMURL.createObjectURL(svg);
    mathimg.src = ""; // Trick from http://code.google.com/p/chromium/issues/detail?id=7731 (Didn't help)
    var drawImg = function() {
        ctx.drawImage(mathimg, 0, 0);
        DOMURL.revokeObjectURL(url);
    };
    mathimg.addEventListener("load", function(e) {
        drawImg();
    }, false);
    mathimg.src = url;
    };
    drawMath();
});
    </script>
  </head>

  <body>
    <canvas id="myCanvas">
      Render some math here
    </canvas>

  </body>
</html>


在Firefox中运行此代码时,将调用图像加载回调。在iPad上加载
不会被调用,也不会渲染。

我尝试了一些操作,包括suggestion,以便在设置回调之前显式设置image.src。

另外,用计时器(300毫秒延迟)替换加载回调似乎也无济于事。代码获取
执行,但仍然没有渲染。由于我的目标平台是iPad,因此这是一个严重的障碍。任何帮助,将不胜感激。

最佳答案

从{type:“ image / svg + xml; charset = utf-8”}中删除“ charset = utf-8”

var svg = new Blob([data], {type: "image/svg+xml"});

关于javascript - 在Safari上在 Canvas 中渲染mathML失败。图像加载回调未触发,我们在Stack Overflow上找到一个类似的问题:https://stackoverflow.com/questions/12789160/

10-12 12:50
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