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| <!DOCTYPE html> | |
| <head> | |
| <meta http-equiv="Content-Type" content="text/html;charset=utf-8"> | |
| <meta http-equiv="encoding" content="utf-8"> | |
| </head> | |
| <canvas id="canvas" width="1490" height="512" style="border:1px dashed"> | |
| CA canvas | |
| </canvas> | |
| <script type="text/javascript"> | |
| var canvas = document.getElementById("canvas"); | |
| </script> | |
| <script type="text/javascript" src="mousetracks.js"></script> | |
| <script type="text/javascript"> | |
| var msecPerFrame = 1000/60; | |
| var nframes = 0; | |
| function step() { | |
| draw(nframes++); | |
| if (canvas.width <= nframes) | |
| clearInterval(frameIntervalId); | |
| } | |
| var frameIntervalId = setInterval(step, msecPerFrame); | |
| </script> |
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| var width = canvas.width, height = canvas.height; | |
| var ctx = canvas.getContext('2d'); | |
| // Midpoint line | |
| var mid = height / 2; | |
| ctx.fillStyle = 'rgba(50, 50, 50, 0.5)'; | |
| ctx.fillRect(0, mid, width, 1); | |
| // Find the canvas top-left. | |
| var canvasLeft = 0, canvasTop = 0; | |
| (function() { | |
| for (var element = canvas; element !== null; element = element.offsetParent) { | |
| canvasLeft += element.offsetLeft; | |
| canvasTop += element.offsetTop; | |
| } | |
| })(); | |
| // Track the mouse coordinates relative to canvas top-left. | |
| var mouseX = 0, mouseY = 0; | |
| canvas.addEventListener('mousemove', function(event) { | |
| mouseX = event.clientX - canvasLeft; | |
| mouseY = event.clientY - canvasTop; | |
| }); | |
| var yPrev = mouseY; | |
| // This gets called repeatedly with x increasing over time. | |
| function draw(x) { | |
| dot(mouseX, mouseY, 1, 'rgba(255, 0, 0, 0.5)'); | |
| dot(x, mouseY, 1, 'black'); | |
| var yVel = mouseY - yPrev; | |
| yPrev = mouseY; | |
| dot(x, mid + yVel, 1, 'rgba(0, 0, 255, 0.5)'); | |
| } | |
| // Plot a circle at (x,y). | |
| function dot(x, y, radius, style) { | |
| ctx.fillStyle = style; | |
| ctx.beginPath(); | |
| ctx.arc(x, y, radius, 0, 2*Math.PI); | |
| ctx.fill(); | |
| } | |
| function wiggle(x) { | |
| var t = x / (width/1.618); | |
| var ft = Math.sin(2*Math.PI*t); | |
| var y = mid - height/3*ft; | |
| dot(x, y, 1, 'rgba(0, 0, 0, 1)'); | |
| var yVel = 10*(y - yPrev); | |
| yPrev = y; | |
| dot(x, mid + yVel, 1, 'rgba(0, 0, 255, 0.5)'); | |
| } | |
| draw = wiggle; // overwrite the draw() function above |
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