65 lines
1.7 KiB
JavaScript
65 lines
1.7 KiB
JavaScript
'use strict';
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import { getColor } from './utils';
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/**
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* Choose an index at random among a list of weights,
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* more weighted indices have a greater proability to be chosen
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*
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* @param {Array} weights List of weights
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* @return {number} Selected index
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*/
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const chooseIndex = weights => {
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const number = Math.random();
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let sum = 0, index = 0;
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while (number >= sum) {
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sum += weights[index];
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index += 1;
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}
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return index - 1;
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};
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/**
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* Apply the chaos game: starting from `start`, we plot
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* the next `n` points. To get to the next point, we apply
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* a random transformation among given ones
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*
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* @param {ImageData} image Image to write on
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* @param {Array} start Starting point
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* @param {number} iterations Number of points to plot
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* @param {Array} transforms List of available transforms
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* @param {Array} weights Probability weights for each transform
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* @return {null}
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*/
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export const applyChaos = (image, start, iterations, transforms, weights) => {
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const width = image.width;
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let point = start;
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if (weights === undefined) {
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weights = Array.apply(null, Array(transforms.length)).map(
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() => 1 / transforms.length
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);
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}
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while (iterations--) {
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const index = chooseIndex(weights);
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const color = getColor(2);
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// console.log(point);
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// console.log(point.map(x => Math.floor(x * 10 + 100)));
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point = transforms[index](point);
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const i = (
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Math.floor(point[1] * 50 + 50) * width +
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Math.floor(point[0] * 50 + 200)
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) * 4;
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image.data[i] = color[0];
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image.data[i + 1] = color[1];
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image.data[i + 2] = color[2];
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image.data[i + 3] = 255;
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}
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};
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