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CSS

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HTML 

              
                <main class="container">
	<h1>Genetic Algorithm to Recreate an Image Using Shapes</h1>
	
	<div class="preview-list">
		<div class="preview-list__item" data-ref="preview"></div>
		<div class="preview-list__item" data-ref="target"></div>
	</div>
	
	<dl>
		<div>
			<dt>Generation</dt>
			<dd data-ref="generation"></dd>
		</div>
		
		<div>
			<dt>Accuracy</dt>
			<dd data-ref="highscore"></dd>
		</div>
		
		<div>
			<dt>Mutation rate</dt>
			<dd data-ref="mutation-rate"></dd>
		</div>
	</dl>
</main>
!

CSS 

              
                canvas {
	display: block;
}

dl {
	display: flex;
	flex-direction: row;
}

dl > div {
	margin-right: 1rem;
}

dt {
	font-weight: bold;
}
dd {
	margin-left: 0;
	margin-bottom: 1rem;
	font-family: monospace;
}

h1 {
	margin-bottom: 1rem;
	margin-top: 0;
}

img {
	display: block;
}

.container {
	margin: 1rem;
}

.preview-list {
	display: flex;
	flex-direction: row;
}
.preview-list__item {
	padding: 0.5rem;
}
!

JS 

              
                const CanvasContextFactory = {
	createContext(width, height) {
		const canvas = document.createElement('canvas');
		
		canvas.height = height;
		canvas.width = width;
		
		return canvas.getContext('2d');
	},
	
	createContextFromImage(image, size) {
		const aspect = image.width / image.height;
		const context = aspect > 1
			? CanvasContextFactory.createContext(size, size / aspect)
			: CanvasContextFactory.createContext(size / aspect, size);
		
		const { height, width } = context.canvas;
		
		context.fillRect(0, 0, width, height);
		context.drawImage(image, 0, 0, width, height);
		
		return context;
	},
	
	createContextFromImageGrayscale(image, size) {
		const context = this.createContextFromImage(image, size);

		const { height, width } = context.canvas;
		const imageData = context.getImageData(0, 0, width, height);
		
		for (let pixelIndex = 0; pixelIndex < width * height; pixelIndex++) {
			const dataIndex = 4 * pixelIndex;
			const luma = ImageDataAnalyzer.getLuma(
				imageData.data[dataIndex + 0],
				imageData.data[dataIndex + 1],
				imageData.data[dataIndex + 2]
			);
			
			imageData.data[dataIndex + 0] = luma;
			imageData.data[dataIndex + 1] = luma;
			imageData.data[dataIndex + 2] = luma;
		}
		
		context.putImageData(imageData, 0, 0);
		
		return context;
	}
};

const ImageDataAnalyzer = {
	getDifference(a, b) {
		const { height, width } = a;
		let difference = 0;
		
		for (let pixelIndex = 0; pixelIndex < width * height; pixelIndex++) {
			const dataIndex = 4 * pixelIndex;
			
			difference += (
				Math.abs(a.data[dataIndex + 0] - b.data[dataIndex + 0]) +
				Math.abs(a.data[dataIndex + 1] - b.data[dataIndex + 1]) +
				Math.abs(a.data[dataIndex + 2] - b.data[dataIndex + 2])
			);
		}
		
		return difference / (width * height * 3 * 255);
	},
	
	getDifferenceGrayscale(a, b) {
		const { height, width } = a;
		let difference = 0;
		
		for (let pixelIndex = 0; pixelIndex < width * height; pixelIndex++) {
			const dataIndex = 4 * pixelIndex;
			
			difference += Math.abs(a.data[dataIndex + 0] - b.data[dataIndex + 0]);
		}
		
		return difference / (width * height * 255);
	},
	
	getLuma(r, g, b) {
		return r * 0.2126 + g * 0.7152 + b * 0.0722;
	},
};

const ImageLoader = {
	load(source) {
		return new Promise((resolve) => {
			const image = new Image();
			
			image.crossOrigin = 'anonymous';
			image.addEventListener('load', () => resolve(image));
			image.src = source;
		});
	},
};

const MathUtils = {
	lerp(a, b, t) {
		return a + t * (b - a);
	},
};

class Circle {
	constructor(
		x = Circle.getRandomX(),
	  y = Circle.getRandomY(),
		z = Circle.getRandomZ(),
		radius = Circle.getRandomRadius(),
		color = Circle.getRandomColor(),
	) {
		this.color = Math.max(0, Math.min(1, color));
		this.colorParsed = Circle.decimalToColor(this.color);
			
		this.radius = radius;
		this.x = x;
		this.y = y;
	}
	
	render(context) {
		const { height, width } = context.canvas;
		const sizeHalf = 0.5 * Math.min(height, width);
		
		context.beginPath();
		context.arc(width * this.x, width * this.y, sizeHalf * this.radius, 0, 2 * Math.PI);
		context.fillStyle = this.colorParsed;
		
		context.fill();
	}
	
	static decimalToColor(decimal) {
		// const hex = Math.floor((0xFFFFFF + 1) * decimal).toString(16).padStart(6, '0');
		
		// return `#${hex}`;
		
		return `hsl(0, 0%, ${100 * decimal}%)`;
	}
	
	static getRandomX() {
		return Math.random();
	}
	
	static getRandomY() {
		return Math.random();
	}
	
	static getRandomZ() {
		return Math.random();
	}
	
	static getRandomRadius() {
		return Math.random();
	}
	
	static getRandomColor() {
		return Math.random();
	}
}

class Organism {
	constructor(circles = Organism.getRandomCircles()) {
		this.circles = circles.sort((a, b) => b.z - a.z);
		this.score = null;
	}
	
	render(context) {
		const { height, width } = context.canvas;
		
		context.fillRect(0, 0, width, height);
		this.circles.forEach(c => c.render(context));
	}
	
	static get CIRCLE_COUNT() {
		return 64;
	}
	
	static getRandomCircles() {
		return Array.from({ length: Organism.CIRCLE_COUNT }, () => new Circle());
	}
}

class Population {
	constructor(size, targetContext) {
		if (size % 2 === 1) {
			throw new Error('This algorithm simulates cellular division to optimize. Please use an even population size.');
		}
		
		const { height, width } = targetContext.canvas;
		
		this.context = CanvasContextFactory.createContext(width, height);
		this.mutationRate = 0.1;
		this.organismList = Array.from({ length: size }, () => new Organism());
		this.populationSize = size;
		this.targetContext = targetContext;
		this.targetImageData = targetContext.getImageData(0, 0, width, height);
	}
	
	createNextPopulation(parents) {
		const organismList = this._getOrganismResultList();
		// const organismElite = this._getOrganismResultList();
		
		this.organismList = [
			...organismList,
			...organismList.map(parent => new Organism(parent.circles.map(circle => new Circle(
				Math.random() < this.mutationRate ? Circle.getRandomX() : circle.x,
				Math.random() < this.mutationRate ? Circle.getRandomY() : circle.y,
				Math.random() < this.mutationRate ? Circle.getRandomZ() : circle.z,
				Math.random() < this.mutationRate ? Circle.getRandomRadius() : circle.radius,
				Math.random() < this.mutationRate ? Circle.getRandomColor() : circle.color,
			))))
			
// 			organismElite,

// 			...Array.from({ length: this.organismList.length - 1 }, () => {
// 				return new Organism(organismElite.circles.map(circle => new Circle(
// 					Math.random() < this.mutationRate ? Circle.getRandomX() : circle.x,
// 					Math.random() < this.mutationRate ? Circle.getRandomY() : circle.y,
// 					Math.random() < this.mutationRate ? Circle.getRandomZ() : circle.z,
// 					Math.random() < this.mutationRate ? Circle.getRandomRadius() : circle.radius,
// 					Math.random() < this.mutationRate ? Circle.getRandomColor() : circle.color,
// 				)));
// 			}),
		];
		
		return this.organismList[0];
	}
	
	_getOrganismResultList(targetImageData) {
		const { height, width } = this.targetContext.canvas;
		
		this.organismList.forEach((organism) => {
			if (organism.score !== null) return;
			
			organism.render(this.context);
			
			const imageData = this.context.getImageData(0, 0, width, height);
			const score = 1 - ImageDataAnalyzer.getDifferenceGrayscale(this.targetImageData, imageData);
			
			organism.score = score;
		});
		
		return Array.from(this.organismList)
			.sort((a, b) => b.score - a.score)
			// .shift();
			.slice(0, 0.5 * this.organismList.length);
	}
}

const createAnimationLoop = (callback) => {
	let frame = 0;

	const update = () => {
		requestAnimationFrame(update);
		callback(frame++);
	};
	
	requestAnimationFrame(update);
};

const URL_IMAGE = 'https://upload.wikimedia.org/wikipedia/commons/thumb/6/67/Firefox_Logo%2C_2017.svg/1024px-Firefox_Logo%2C_2017.svg.png';

const elementGeneration = document.querySelector('[data-ref="generation"]');
const elementHighscore = document.querySelector('[data-ref="highscore"]');
const elementMutationRate = document.querySelector('[data-ref="mutation-rate"]');

(async () => {
	const image = await ImageLoader.load(URL_IMAGE);
	const contextImage = CanvasContextFactory.createContextFromImageGrayscale(image, 128);
	const contextPreview = CanvasContextFactory.createContext(
		contextImage.canvas.width,
		contextImage.canvas.height);
	
	const population = new Population(16, contextImage);
	let result;
	
	document.querySelector('[data-ref="preview"]').appendChild(contextImage.canvas);
	document.querySelector('[data-ref="target"]').appendChild(contextPreview.canvas);
	
	createAnimationLoop((frame) => {
		const organism = population.createNextPopulation();
		
		organism.render(contextPreview);
		population.mutationRate = MathUtils.lerp(0.5, 0.2, Math.pow(organism.score, 2));
		
		elementGeneration.textContent = frame;
		elementHighscore.textContent = organism.score.toFixed(10);
		elementMutationRate.textContent = population.mutationRate;
	});
})();
!
999px

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