The d3.interpolateCubehelix plugin implements Dave Green’s cubehelix color scheme. The color ramp above is the default configuration of cubehelix, but the scheme is highly configurable; see the other examples.
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February 9, 2016 01:55
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Cubehelix
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| license: gpl-3.0 |
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| (function() { | |
| var radians = Math.PI / 180; | |
| d3.scale.cubehelix = function() { | |
| return d3.scale.linear() | |
| .range([d3.hsl(300, .5, 0), d3.hsl(-240, .5, 1)]) | |
| .interpolate(d3.interpolateCubehelix); | |
| }; | |
| d3.interpolateCubehelix = d3_interpolateCubehelix(1); | |
| d3.interpolateCubehelix.gamma = d3_interpolateCubehelix; | |
| function d3_interpolateCubehelix(γ) { | |
| return function(a, b) { | |
| a = d3.hsl(a); | |
| b = d3.hsl(b); | |
| var ah = (a.h + 120) * radians, | |
| bh = (b.h + 120) * radians - ah, | |
| as = a.s, | |
| bs = b.s - as, | |
| al = a.l, | |
| bl = b.l - al; | |
| if (isNaN(bs)) bs = 0, as = isNaN(as) ? b.s : as; | |
| if (isNaN(bh)) bh = 0, ah = isNaN(ah) ? b.h : ah; | |
| return function(t) { | |
| var h = ah + bh * t, | |
| l = Math.pow(al + bl * t, γ), | |
| a = (as + bs * t) * l * (1 - l); | |
| return "#" | |
| + hex(l + a * (-0.14861 * Math.cos(h) + 1.78277 * Math.sin(h))) | |
| + hex(l + a * (-0.29227 * Math.cos(h) - 0.90649 * Math.sin(h))) | |
| + hex(l + a * (+1.97294 * Math.cos(h))); | |
| }; | |
| }; | |
| } | |
| function hex(v) { | |
| var s = (v = v <= 0 ? 0 : v >= 1 ? 255 : v * 255 | 0).toString(16); | |
| return v < 0x10 ? "0" + s : s; | |
| } | |
| })(); |
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| <!DOCTYPE html> | |
| <meta charset="utf-8"> | |
| <style> | |
| canvas { | |
| width: 960px; | |
| height: 500px; | |
| } | |
| </style> | |
| <canvas width="960" height="1"> | |
| <script src="//d3js.org/d3.v3.min.js"></script> | |
| <script src="cubehelix.js"></script> | |
| <script> | |
| var canvas = document.querySelector("canvas"), | |
| width = canvas.width, | |
| color = d3.scale.cubehelix().domain([0, width - 1]), | |
| context = canvas.getContext("2d"), | |
| image = context.createImageData(width, 1); | |
| for (var i = 0, j = -1, c; i < width; ++i) { | |
| c = d3.rgb(color(i)); | |
| image.data[++j] = c.r; | |
| image.data[++j] = c.g; | |
| image.data[++j] = c.b; | |
| image.data[++j] = 255; | |
| } | |
| context.putImageData(image, 0, 0); | |
| </script> |
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