Convert SVG to Retina Canvas

Convert SVG to canvas on-the-fly. Updated to support higher pixel densities, like Retina displays. Compare to Andrew Mollica's example which looks slightly fuzzy on high-density displays.

This article from MDN explains the process: Drawing DOM object into a canvas. This works for any DOM object, not just SVG. Not sure if this is well supported by older browsers. Works on Chrome, Firefox and IE 10 for me. The bar chart is a fork of this block by Mike Bostock: Canvas Bar Chart.

<html>
<head>
<style>
/* Any styling on the SVG won't transfer to the Canvas */
/* Styling must be done inline */
</style>
</head>
<body>
<script src="https://d3js.org/d3.v4.min.js"></script>
<script>

var margin = { top: 20, right: 20, bottom: 30, left: 40 },
		width = 960 - margin.left - margin.right,
		height = 500 - margin.top - margin.bottom;

var x = d3.scaleBand()
	.rangeRound([0, width])
	.padding(0.1);

var y = d3.scaleLinear()
	.rangeRound([height, 0]);

var svg = d3.select("body").append("svg")
	.attr("xmlns", "https://www.w3.org/2000/svg")
	.attr("width", width + margin.left + margin.right)
	.attr("height", height + margin.top + margin.bottom);

var g = svg.append("g")
	.attr("transform", "translate(" + margin.left + "," + margin.top + ")");

var devicePixelRatio = window.devicePixelRatio || 1;

var canvas = d3.select("body").append("canvas")
  .attr("width", (width + margin.left + margin.right) * devicePixelRatio)
  .attr("height", (height + margin.top + margin.bottom) * devicePixelRatio)
  .style("width", width + "px")
  .style("height", height + "px")
  .style("margin-top", margin.top + "px")
  .style("margin-left", margin.left + "px");

var context = canvas.node().getContext("2d");
context.scale(devicePixelRatio, devicePixelRatio);

d3.tsv("data.tsv", processRow, function(error, data) {
	if (error) throw error;

// Update scales
	x.domain(data.map(function(d) { return d.letter; }));
	y.domain([0, d3.max(data, function(d) { return d.frequency; })]);

// Draw axes
	g.append("g")
		.attr("class", "axis axis--x")
		.attr("transform", "translate(0," + height + ")")
		.call(d3.axisBottom(x))
		.select("path")
		.style("stroke", "none");
	
	g.append("g")
			.attr("class", "axis axis--y")
			.call(d3.axisLeft(y).tickFormat(d3.format(".0%")))
		.append("text")
			.attr("transform", "rotate(-90)")
			.attr("dx", "-1em")
			.attr("dy", "1.66em")
			.style("fill", "#000")
			.text("Frequency");
	
	// Draw bars
	g.append("g")
			.attr("class", "bars")
		.selectAll(".bar").data(data)
		.enter().append("rect")
			.attr("class", "bar")
			.attr("x", function(d) { return x(d.letter); })
			.attr("y", function(d) { return y(d.frequency); })
			.attr("width", x.bandwidth())
			.attr("height", function(d) { return height - y(d.frequency); })
			.style("fill", "steelblue");

// Convert SVG to Canvas
	// see: https://developer.mozilla.org/en-US/docs/Web/API/Canvas_API/Drawing_DOM_objects_into_a_canvas
	var DOMURL = window.URL || window.webkitURL || window;

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

image.onload = function() {
		context.drawImage(image, 0, 0);
		DOMURL.revokeObjectURL(url);
	}

image.src = url;
});

function processRow(d) {
	d.frequency = +d.frequency;
	return d;
}

// Get the string representation of a DOM node (removes the node)
function domNodeToString(domNode) {
	var element = document.createElement("div");
	element.appendChild(domNode);
	return element.innerHTML;
}

</script>
</body>
</html>

https://d3js.org/d3.v4.min.js