53 lines
1.6 KiB
JavaScript
53 lines
1.6 KiB
JavaScript
"use strict";
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var page = require('webpage').create();
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page.viewportSize = { width: 400, height : 400 };
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page.content = '<html><body><canvas id="surface"></canvas></body></html>';
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page.evaluate(function() {
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var el = document.getElementById('surface'),
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context = el.getContext('2d'),
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width = window.innerWidth,
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height = window.innerHeight,
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cx = width / 2,
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cy = height / 2,
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radius = width / 2.3,
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imageData,
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pixels,
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hue, sat, value,
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i = 0, x, y, rx, ry, d,
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f, g, p, u, v, w, rgb;
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el.width = width;
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el.height = height;
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imageData = context.createImageData(width, height);
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pixels = imageData.data;
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for (y = 0; y < height; y = y + 1) {
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for (x = 0; x < width; x = x + 1, i = i + 4) {
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rx = x - cx;
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ry = y - cy;
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d = rx * rx + ry * ry;
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if (d < radius * radius) {
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hue = 6 * (Math.atan2(ry, rx) + Math.PI) / (2 * Math.PI);
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sat = Math.sqrt(d) / radius;
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g = Math.floor(hue);
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f = hue - g;
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u = 255 * (1 - sat);
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v = 255 * (1 - sat * f);
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w = 255 * (1 - sat * (1 - f));
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pixels[i] = [255, v, u, u, w, 255, 255][g];
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pixels[i + 1] = [w, 255, 255, v, u, u, w][g];
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pixels[i + 2] = [u, u, w, 255, 255, v, u][g];
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pixels[i + 3] = 255;
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}
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}
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}
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context.putImageData(imageData, 0, 0);
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document.body.style.backgroundColor = 'white';
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document.body.style.margin = '0px';
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});
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page.render('colorwheel.png');
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phantom.exit();
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