How to render a d3.js map on canvas free of blurriness - html

Question

Try as I might, I've been unable to render a d3.js county map without causing the map to blur significantly.
I'm using the usual tricks: My canvas style width is half that of my attribute width. I translate the context of the drawing half a pixel to offset any unwanted effects.
But it's still terribly blurry.
Can someone share the pattern for a crisp d3.js map made for canvas elements?
function drawQuintiles() {
var width = 960,
height = 500;
var projection = d3.geo.albers()
.scale(666);
var canvas = d3.select("#quintiles")
.append("canvas")
.attr("class",'canvasarea');
var context = canvas.node().getContext("2d");
var ratio = (window.devicePixelRatio / context.webkitBackingStorePixelRatio) || 1;
d3.select('.canvasarea')
.attr("width", width * ratio).attr("height", height * ratio)
.style("width", width + "px").style("height", height + "px");
context.scale(ratio, ratio);
var path = d3.geo.path()
.projection(projection)
.context(context);
d3.json("/data/us-counties.json", function(error, us) {
if (error) throw error;
context.strokeStyle = '#333';
context.beginPath();
var strokeWidth = 0.5;
var iTranslate = (strokeWidth % 2) / 2;
context.translate(iTranslate, 0);
context.lineWidth = strokeWidth;
context.lineCap = "round";
path(topojson.feature(us, us.objects.counties));
context.stroke();
});
}

Answer 1

This is the code I ended on. Removing the scale and the translate hack has the map rendering properly.
function drawQuintiles() {
var width = 1600;
d3.json("/data/us-counties.json", function(error, data) {
var projection = d3.geo.albersUsa();
var path = d3.geo.path().projection(projection);
var tracts = topojson.feature(data, data.objects.counties);
projection.scale(1).translate([0, 0]);
var b = path.bounds(tracts);
var whRatio = ((b[1][0] - b[0][0]) / (b[1][1] - b[0][1]));
var height = (width / 2) * whRatio;
var s = .98 / Math.max((b[1][0] - b[0][0]) / width, (b[1][1] - b[0][1]) / height),
t = [(width - s * (b[1][0] + b[0][0])) / 2, (height - s * (b[1][1] + b[0][1])) / 2];
projection.scale(s).translate(t);
var canvas = d3.select("#quintiles")
.append("canvas")
.attr("class",'canvasarea');
var context = canvas.node().getContext("2d");
var ratio = window.devicePixelRatio || 1;
d3.select('.canvasarea')
.attr("width", width ).attr("height", height )
.style("width", ((width * ratio) ) + "px").style("height", ((height * ratio) ) + "px");
var path = d3.geo.path()
.projection(projection)
.context(context);
if (error) throw error;
context.strokeStyle = '#333';
context.beginPath();
var strokeWidth = 0.5;
context.lineWidth = strokeWidth;
context.lineCap = "round";
path(topojson.feature(data, data.objects.counties));
context.stroke();
});
}
drawQuintiles();