This is a little script I wrote to visualize mathematical functions.
plot(function(x) { return Math.sin(x); });plot2d(function(x, y) { return y*y + x*x > 100*100; });
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August 29, 2015 14:15
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Simple HTML Canvas Function Plotter
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| <!DOCTYPE html> | |
| <html> | |
| <head> | |
| <title>Function Plotter</title> | |
| <script type="text/javascript"> | |
| function plot(func) { | |
| var canvas = document.getElementById('canvas'); | |
| var ctx = canvas.getContext('2d'); | |
| var axes = { | |
| x0: 0.5 + 0.5 * canvas.width, | |
| y0: 0.5 + 0.5 * canvas.height, | |
| scale: 40, | |
| doNegativeX: true | |
| }; | |
| showAxes(ctx, axes); | |
| graph(ctx, axes, func, 'hsl(' + Math.floor(Math.random()*360) + ',100%,50%)', 1); | |
| } | |
| function graph(ctx, axes, func, color, thick) { | |
| var xx, yy, dx = 4, | |
| x0 = axes.x0, | |
| y0 = axes.y0, | |
| scale = axes.scale; | |
| var iMax = Math.round((ctx.canvas.width - x0) / dx); | |
| var iMin = axes.doNegativeX ? Math.round(-x0 / dx) : 0; | |
| ctx.beginPath(); | |
| ctx.lineWidth = thick; | |
| ctx.strokeStyle = color; | |
| for (var i = iMin; i <= iMax; i++) { | |
| xx = dx * i; | |
| yy = scale * func(xx / scale); | |
| if (i == iMin) ctx.moveTo(x0 + xx, y0 - yy); | |
| else ctx.lineTo(x0 + xx, y0 - yy); | |
| } | |
| ctx.stroke(); | |
| } | |
| function showAxes(ctx, axes) { | |
| var x0 = axes.x0, | |
| w = ctx.canvas.width; | |
| var y0 = axes.y0, | |
| h = ctx.canvas.height; | |
| var xmin = axes.doNegativeX ? 0 : x0; | |
| ctx.beginPath(); | |
| ctx.strokeStyle = '#555'; | |
| ctx.moveTo(xmin, y0); | |
| ctx.lineTo(w, y0); | |
| ctx.moveTo(x0, 0); | |
| ctx.lineTo(x0, h); | |
| ctx.stroke(); | |
| } | |
| function plot2d(func) { | |
| var canvas = document.getElementById('canvas'); | |
| ctx = canvas.getContext('2d'); | |
| var data = ctx.createImageData(canvas.width, canvas.height); | |
| var pixels = data.data; | |
| var x, y; | |
| for (var i = 0; i < pixels.length; i += 4) { | |
| x = ((i / 4) % canvas.width) - (canvas.width / 2); | |
| y = (canvas.height / 2) - Math.floor((i / 4) / canvas.width); | |
| var draw = func(x, y); | |
| pixels[i] = draw ? 0 : 255; | |
| pixels[i + 1] = draw ? 0 : 255; | |
| pixels[i + 2] = draw ? 0 : 255; | |
| pixels[i + 3] = 255; | |
| } | |
| ctx.putImageData(data, 0, 0); | |
| return pixels; | |
| } | |
| </script> | |
| </head> | |
| <body> | |
| <canvas id="canvas" width="512" height="512" style="background: #eee; border: 1px solid #555"></canvas> | |
| </body> | |
| </html> |
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