863D3 canvas and Retina screens
function getRetinaRatio() {
var devicePixelRatio = window.devicePixelRatio || 1
var c = document.createElement('canvas').getContext('2d')
var backingStoreRatio = [
c.webkitBackingStorePixelRatio,
c.mozBackingStorePixelRatio,
c.msBackingStorePixelRatio,
c.oBackingStorePixelRatio,
c.backingStorePixelRatio,
1
].reduce(function(a, b) { return a || b })
return devicePixelRatio / backingStoreRatio}
var ratio = getRetinaRatio() var scaledWidth = width ratio var scaledHeight = height ratio