使用javascript未知DOM异常将SVG保存为PNG

Question

I am trying to convert an SVG to PNG through browser using javascript
I've been following the answer on this question Save inline SVG as JPEG/PNG/SVG

It works for the given XML in that answer Unfortunately, I got Uncaught DOMException: Failed to execute 'toDataURL' on 'HTMLCanvasElement': Tainted canvases may not be exported. when trying to convert my SVG. Here's the snippet to my code. Can anybody tell me why it's not working?

 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

You have issues in your SVG's foreignObject on removing this will solve your issue,

 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> 

You can also try Canvas2Image plugin