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March 25, 2016 14:40
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Astigmatism eye test (see live: https://goo.gl/TVVnVO)
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| <!DOCTYPE html> | |
| <html> | |
| <head> | |
| <meta charset="utf-8"> | |
| <title>Astigmatism eye test</title> | |
| <style> | |
| canvas { | |
| position: fixed; | |
| top: 0; | |
| left: 0; | |
| width: 100%; | |
| height: 100%; | |
| background-color: black; | |
| } | |
| </style> | |
| <script> | |
| var angle = 0; | |
| var radius = 20; | |
| var tile, tileCtx, ctx; | |
| onload = function() { | |
| tile = document.createElement('canvas'); | |
| tileCtx = tile.getContext('2d'); | |
| ctx = canvas.getContext('2d'); | |
| draw(); | |
| }; | |
| function draw() { | |
| tile.width = tile.height = radius * 2; | |
| tileCtx.strokeStyle = '#fff'; | |
| tileCtx.lineWidth = Math.max(1, radius / 6); | |
| tileCtx.translate(radius, radius); | |
| tileCtx.rotate(angle / 180 * Math.PI); | |
| tileCtx.beginPath(); | |
| tileCtx.moveTo(-radius / 2, 0); | |
| tileCtx.lineTo(radius / 2, 0); | |
| tileCtx.stroke(); | |
| var pattern = ctx.createPattern(tile, 'repeat'); | |
| canvas.width = window.innerWidth; | |
| canvas.height = window.innerHeight; | |
| ctx.save(); | |
| var offsetX = canvas.width / 2 + tile.width / 2; | |
| var offsetY = canvas.height / 2 + tile.height / 2; | |
| ctx.translate(offsetX, offsetY); | |
| ctx.fillStyle = pattern; | |
| ctx.fillRect(-offsetX, -offsetY, canvas.width, canvas.height); | |
| ctx.restore(); | |
| ctx.fillStyle = '#888'; | |
| ctx.font = "700 20px courier"; | |
| ctx.fillText("axis: " + (0 | (angle + 90) % 180) + "\u00B0", 10, 30); | |
| } | |
| onmousemove = function(event) { | |
| angle = event.offsetX / window.innerWidth * 180 * 2; | |
| draw(); | |
| }; | |
| onkeyup = function(event) { | |
| switch (event.keyIdentifier) { | |
| case "Up": | |
| case "U+004B": | |
| radius *= 1.5; | |
| break; | |
| case "Down": | |
| case "U+004D": | |
| radius /= 1.5; | |
| break; | |
| case "Left": | |
| angle -= 1; | |
| angle |= 0; | |
| break; | |
| case "Right": | |
| angle += 1; | |
| angle |= 0; | |
| break; | |
| default: | |
| } | |
| draw(); | |
| }; | |
| </script> | |
| </head> | |
| <body> | |
| <canvas id="canvas" /> | |
| </body> | |
| </html> |
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