javascript - 使用 javascript 将 SVG 保存为 PNG 未知 DOM 异常

Question

我正在尝试使用 javascript 通过浏览器将 SVG 转换为 PNG
我一直在关注这个问题的答案Save inline SVG as JPEG/PNG/SVG

它适用于该答案中给定的 XML 不幸的是，我在尝试转换 SVG 时遇到了 Uncaught DOMException: Failed toexecute 'toDataURL' on 'HTMLCanvasElement': Tainted canvases may not be Export.。这是我的代码片段。谁能告诉我为什么它不起作用？

var btn = document.querySelector('button');
var svg = document.querySelector('svg');
var canvas = document.querySelector('canvas');

function triggerDownload (imgURI) {
  var evt = new MouseEvent('click', {
    view: window,
    bubbles: false,
    cancelable: true
  });

  var a = document.createElement('a');
  a.setAttribute('download', 'MY_COOL_IMAGE.png');
  a.setAttribute('href', imgURI);
  a.setAttribute('target', '_blank');

  a.dispatchEvent(evt);
}

btn.addEventListener('click', function () {
  var canvas = document.getElementById('canvas');
  var ctx = canvas.getContext('2d');
  var data = (new XMLSerializer()).serializeToString(svg);
  var DOMURL = window.URL || window.webkitURL || window;

  var img = new Image();
  img.crossOrigin = 'anonymous'

  var svgBlob = new Blob([data], {type: 'image/svg+xml;charset=utf-8'});
  var url = DOMURL.createObjectURL(svgBlob);

  img.onload = function () {
    ctx.drawImage(img, 0, 0);
    DOMURL.revokeObjectURL(url);

    var imgURI = canvas
        .toDataURL('image/png')
        .replace('image/png', 'image/octet-stream');

    triggerDownload(imgURI);
  };

  img.src = url;
});

<button>svg to png</button>

<svg xmlns="http://www.w3.org/2000/svg" xmlns:xlink="http://www.w3.org/1999/xlink" width="161px" height="91px" version="1.1" style="background-color: rgb(255, 255, 255);"><defs/><g transform="translate(0.5,0.5)"><rect x="0" y="0" width="160" height="90" fill="#ffffff" stroke="#000000" pointer-events="none"/><path d="M 0 26 L 0 0 L 160 0 L 160 26 Z" fill="#dae8fc" stroke="#000000" stroke-miterlimit="10" pointer-events="none"/><g transform="translate(48.5,7.5)"><switch><foreignObject style="overflow:visible;" pointer-events="all" width="63" height="12" requiredFeatures="http://www.w3.org/TR/SVG11/feature#Extensibility"><div xmlns="http://www.w3.org/1999/xhtml" style="display: inline-block; font-size: 12px; font-family: Helvetica; color: rgb(0, 0, 0); line-height: 1.2; vertical-align: top; white-space: nowrap; font-weight: bold; text-align: center;"><div xmlns="http://www.w3.org/1999/xhtml" style="display:inline-block;text-align:inherit;text-decoration:inherit;">Classname</div></div></foreignObject><text x="32" y="12" fill="#000000" text-anchor="middle" font-size="12px" font-family="Helvetica" font-weight="bold">Classname</text></switch></g><g transform="translate(5.5,32.5)"><switch><foreignObject style="overflow:visible;" pointer-events="all" width="62" height="12" requiredFeatures="http://www.w3.org/TR/SVG11/feature#Extensibility"><div xmlns="http://www.w3.org/1999/xhtml" style="display: inline-block; font-size: 12px; font-family: Helvetica; color: rgb(0, 0, 0); line-height: 1.2; vertical-align: top; overflow: hidden; max-height: 22px; max-width: 148px; width: 63px; white-space: normal; word-wrap: normal;"><div xmlns="http://www.w3.org/1999/xhtml" style="display:inline-block;text-align:inherit;text-decoration:inherit;">+ field: type</div></div></foreignObject><text x="31" y="12" fill="#000000" text-anchor="middle" font-size="12px" font-family="Helvetica">+ field: type</text></switch></g><path d="M 0 56 L 160 56" fill="none" stroke="#000000" stroke-miterlimit="10" pointer-events="none"/><g transform="translate(5.5,66.5)"><switch><foreignObject style="overflow:visible;" pointer-events="all" width="111" height="12" requiredFeatures="http://www.w3.org/TR/SVG11/feature#Extensibility"><div xmlns="http://www.w3.org/1999/xhtml" style="display: inline-block; font-size: 12px; font-family: Helvetica; color: rgb(0, 0, 0); line-height: 1.2; vertical-align: top; overflow: hidden; max-height: 22px; max-width: 148px; width: 112px; white-space: normal; word-wrap: normal;"><div xmlns="http://www.w3.org/1999/xhtml" style="display:inline-block;text-align:inherit;text-decoration:inherit;">+ method(type): type</div></div></foreignObject><text x="56" y="12" fill="#000000" text-anchor="middle" font-size="12px" font-family="Helvetica">+ method(type): type</text></switch></g></g></svg>

<canvas id="canvas"></canvas>

Answer 1

您的 SVG 的 foreignObject 存在问题，删除它即可解决您的问题，

var btn = document.querySelector('button');
var svg = document.querySelector('svg');
var canvas = document.querySelector('canvas');

function triggerDownload (imgURI) {
  var evt = new MouseEvent('click', {
    view: window,
    bubbles: false,
    cancelable: true
  });

  var a = document.createElement('a');
  a.setAttribute('download', 'MY_COOL_IMAGE.png');
  a.setAttribute('href', imgURI);
  a.setAttribute('target', '_blank');

  a.dispatchEvent(evt);
}

btn.addEventListener('click', function () {
  var canvas = document.getElementById('canvas');
  var ctx = canvas.getContext('2d');
  var data = (new XMLSerializer()).serializeToString(svg);
  var DOMURL = window.URL || window.webkitURL || window;

  var img = new Image();
  img.crossOrigin = 'anonymous'

  var svgBlob = new Blob([data], {type: 'image/svg+xml;charset=utf-8'});
  var url = DOMURL.createObjectURL(svgBlob);

  img.onload = function () {
    ctx.drawImage(img, 0, 0);
    DOMURL.revokeObjectURL(url);

    var imgURI = canvas
        .toDataURL('image/png')
        .replace('image/png', 'image/octet-stream');

    triggerDownload(imgURI);
  };

  img.src = url;
});

<button>svg to png</button>

<svg xmlns="http://www.w3.org/2000/svg" xmlns:xlink="http://www.w3.org/1999/xlink" width="161px" height="91px" version="1.1" style="background-color: rgb(255, 255, 255);">
<defs/>
<g transform="translate(0.5,0.5)">
<rect x="0" y="0" width="160" height="90" fill="#ffffff" stroke="#000000" pointer-events="none"/>
<path d="M 0 26 L 0 0 L 160 0 L 160 26 Z" fill="#dae8fc" stroke="#000000" stroke-miterlimit="10" pointer-events="none"/>
<g transform="translate(48.5,7.5)">
<switch>

<text x="32" y="12" fill="#000000" text-anchor="middle" font-size="12px" font-family="Helvetica" font-weight="bold">Classname</text>
</switch>
</g>
<g transform="translate(5.5,32.5)">
<switch>


<text x="31" y="12" fill="#000000" text-anchor="middle" font-size="12px" font-family="Helvetica">+ field: type</text>
</switch>
</g>
<path d="M 0 56 L 160 56" fill="none" stroke="#000000" stroke-miterlimit="10" pointer-events="none"/><g transform="translate(5.5,66.5)">
<switch>

<text x="56" y="12" fill="#000000" text-anchor="middle" font-size="12px" font-family="Helvetica">+ method(type): type</text>
</switch>
</g>
</g>
</svg>

<canvas id="canvas"></canvas>

您也可以尝试Canvas2Image plugin