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January 4, 2021 16:42
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High DPI Canvas (Retina support)
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| var width = 500, | |
| height = 70, | |
| font = '18px serif' | |
| 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 | |
| var blurredCanvas = d3.select('body').append('canvas') | |
| .attr('width', scaledWidth / 2) | |
| .attr('height', scaledHeight / 2) | |
| .style('width', width + 'px') | |
| .style('height', height + 'px') | |
| var goodCanvas = d3.select('body').append('canvas') | |
| .attr('width', scaledWidth) | |
| .attr('height', scaledHeight) | |
| .style('width', width + 'px') | |
| .style('height', height + 'px') | |
| var blurredContext = blurredCanvas.node().getContext('2d') | |
| blurredContext.scale(ratio / 2, ratio / 2) | |
| blurredContext.font = font | |
| blurredContext.fillText("Half of native scale. Blurred image.", 10, 20) | |
| blurredContext.fillText("This happens when you forget about retina screens.", 10, 45) | |
| var goodContext = goodCanvas.node().getContext('2d') | |
| goodContext.scale(ratio, ratio) | |
| goodContext.font = font | |
| goodContext.fillText("Native scale. Exact pixel match.", 10, 20) | |
| goodContext.fillText("Show some respect to users, scale your canvas!", 10, 45) |
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| <html> | |
| <head> | |
| <meta charset="utf-8"> | |
| <style> | |
| body { | |
| margin: 0; | |
| } | |
| canvas { | |
| float: left; | |
| clear: left; | |
| } | |
| </style> | |
| </head> | |
| <body> | |
| <script src="http://d3js.org/d3.v3.min.js"></script> | |
| <script src="canvas.js"></script> | |
| <script>d3.select(self.frameElement).style("height", "140px")</script> | |
| </body> | |
| </html> |
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