function putAnImageInTheCanvas() {
var svg = document.createElementNS('http://www.w3.org/2000/svg', 'svg');
var svgNS = svg.namespaceURI;
svg.setAttribute('xmlns', 'http://www.w3.org/2000/svg');
svg.setAttribute('xmlns:xlink', 'http://www.w3.org/1999/xlink');
svg.setAttribute('height', '310');
svg.setAttribute('width', '310');
svg.setAttribute('version', '1.1');
var svgRect = document.createElementNS(svgNS, 'rect');
svgRect.setAttribute('x', '125');
svgRect.setAttribute('y', '25');
svgRect.setAttribute('height', '250');
svgRect.setAttribute('width', '50');
svgRect.setAttribute('fill', 'rgb(0,255,255)');
svg.appendChild(svgRect);
var dataSrc = 'data:image/svg+xml;base64,' + btoa(svg.outerHTML);
var img = document.createElement('img');
img.setAttribute('src', dataSrc);
var c = document.getElementById('myCanvas');
var ctx = c.getContext("2d");
img.addEventListener('load', function() {
ctx.drawImage(img, 0, 0, 310, 310, 0, 0, 310, 310);
});
}
function render(darwBackground) {
var myCanvas = document.getElementById('myCanvas');
var svg = document.createElementNS('http://www.w3.org/2000/svg', 'svg');
var svgNS = svg.namespaceURI;
svg.setAttribute('xmlns', 'http://www.w3.org/2000/svg');
svg.setAttribute('xmlns:xlink', 'http://www.w3.org/1999/xlink');
svg.setAttribute('height', '310');
svg.setAttribute('width', '310');
svg.setAttribute('version', '1.1');
var background = document.getElementById('main').cloneNode();
background.setAttribute("xmlns", document.documentElement.namespaceURI);
var svgFO_BG = document.createElementNS(svgNS, 'foreignObject');
svgFO_BG.setAttribute('height', '310');
svgFO_BG.setAttribute('width', '310');
svgFO_BG.setAttribute('x', '0');
svgFO_BG.setAttribute('y', '0');
svgFO_BG.innerHTML = background.outerHTML.replace(/(\r\n|\n|\r|\t|[\s]{2,})/gm, '');
var back = document.getElementById('back').cloneNode(true);
back.setAttribute("xmlns", document.documentElement.namespaceURI);
var svgFO_AB = document.createElementNS(svgNS, 'foreignObject');
svgFO_AB.setAttribute('height', '310');
svgFO_AB.setAttribute('width', '310');
svgFO_AB.setAttribute('x', '0');
svgFO_AB.setAttribute('y', '0');
svgFO_AB.innerHTML = back.outerHTML.replace(/(\r\n|\n|\r|\t|[\s]{2,})/gm, '');
var front = document.getElementById('front').cloneNode(true);
front.setAttribute("xmlns", document.documentElement.namespaceURI);
var svgFO_AA = document.createElementNS(svgNS, 'foreignObject');
svgFO_AA.setAttribute('height', '310');
svgFO_AA.setAttribute('width', '310');
svgFO_AA.setAttribute('x', '0');
svgFO_AA.setAttribute('y', '0');
svgFO_AA.innerHTML = front.outerHTML.replace(/(\r\n|\n|\r|\t|[\s]{2,})/gm, '');
var svgImage = document.createElementNS(svgNS, 'image');
svgImage.setAttribute('xlink:href', myCanvas.toDataURL());
svgImage.setAttribute('x', '0');
svgImage.setAttribute('y', '0');
svgImage.setAttribute('height', '310');
svgImage.setAttribute('width', '310');
var g = document.createElementNS(svgNS, 'g');
if (darwBackground) {
g.appendChild(svgFO_BG);
svg.appendChild(g);
}
g = document.createElementNS(svgNS, 'g');
g.appendChild(svgFO_AB);
svg.appendChild(g);
g = document.createElementNS(svgNS, 'g');
g.appendChild(svgImage);
svg.appendChild(g);
g = document.createElementNS(svgNS, 'g');
g.appendChild(svgFO_AA);
svg.appendChild(g);
var data = svg.outerHTML;
document.getElementById('renderOutput').innerHTML = data;
}
<input type="button" value="load canvas image" onclick="putAnImageInTheCanvas();" />
<input type="button" value="render with background" onclick="render(true);" />
<input type="button" value="render without background" onclick="render(false);" />
<h2>Preview:</h2>
<div id="main" style="border: 5px blue solid; width: 300px; height: 300px; background: yellow; position: relative; top: 0; left: 0; overflow: hidden;">
<canvas id="myCanvas" height="300px" width="300px" style="display: block; position: absolute; top: 0; left: 0; z-index: 1;"></canvas>
<div id="back" style="position: relative; top: 0; left: 0;">
<div style=" width: 100px; position: absolute; top: 75px; left: 75px; font-size: 20px; font-family: times; z-index: 0;">
<div style="background: orange;">BACK</div>
</div>
</div>
<div id="front" style="position: relative; top: 0; left: 0;">
<div style=" width: 100px; position: absolute; top: 150px; left: 150px; font-size: 20px; font-family: times; z-index: 2;">
<div style="background: lime;">FRONT</div>
</div>
</div>
</div>
<h2>Render Result:</h2>
<div id="renderOutput">
</div>