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December 24, 2015 00:29
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Laserpointer with canvas
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| <html> | |
| <head> | |
| <script> | |
| var canvas; | |
| var points = []; | |
| var timer; | |
| var mousePos; | |
| var prevPos; | |
| function start() { | |
| canvas = document.getElementById("canvas"); | |
| timer = setInterval(update, 20); | |
| window.onmousemove = handleMouseMove; | |
| mousePos = null; | |
| prevPos = null; | |
| } | |
| function update() { | |
| // samplePointer(); | |
| // redraw(); | |
| points.splice(0, 2); | |
| redraw(); | |
| } | |
| function samplePointer() { | |
| if (mousePos === null) { | |
| return; | |
| } | |
| console.log(prevPos, mousePos); | |
| } | |
| function redraw() { | |
| if (canvas.getContext) { | |
| canvas.width = window.innerWidth; | |
| canvas.height = window.innerHeight; | |
| var ctx = canvas.getContext('2d'); | |
| drawCurve(ctx, points); | |
| } | |
| } | |
| function handleMouseMove(event) { | |
| event = event || window.event; // IE-ism | |
| prevPos = mousePos; | |
| mousePos = { | |
| x: event.clientX, | |
| y: event.clientY | |
| }; | |
| if (prevPos != null && prevPos.x == mousePos.x && prevPos.y == mousePos.y) { | |
| return; | |
| } | |
| points.push(mousePos.x); | |
| points.push(mousePos.y); | |
| if (points.length > 60) { | |
| points.splice(0, 2); | |
| } | |
| redraw(); | |
| } | |
| function drawCurve(ctx, pts) { | |
| ctx.beginPath(); | |
| drawLines(ctx, pts); | |
| ctx.strokeStyle = "rgb(255, 0, 0)"; | |
| ctx.lineWidth = 6; | |
| ctx.stroke(); | |
| ctx.restore(); | |
| } | |
| function drawLines(ctx, ppts) { | |
| ctx.moveTo(ppts[0], ppts[1]); | |
| for (var i = 0; i < ppts.length - 4; i += 2) { | |
| var c = (ppts[i] + ppts[i+2]) / 2; | |
| var d = (ppts[i+1] + ppts[i+3]) / 2; | |
| ctx.quadraticCurveTo(ppts[i], ppts[i+1], c, d); | |
| } | |
| } | |
| </script> | |
| </head> | |
| <body onload="start()" onresize="redraw()"> | |
| <canvas id="canvas"></canvas> | |
| </body> | |
| </html> |
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