jake-sl/index.html

## index.html
<body>
    <input type="file" id="image-input" accept="image/*">
    <input type="range" id="hue-range" min="0" max="360" value="0">
    <input type="color" id="bg-color" value="#ffffff">
    <canvas id="image-canvas"></canvas>
    <script src="main.js"></script>
</body>

## script.js
const imageInput = document.getElementById('image-input');
const hueRange = document.getElementById('hue-range');
const bgColor = document.getElementById('bg-color');
const canvas = document.getElementById('image-canvas');
const ctx = canvas.getContext('2d');
let img = new Image();

imageInput.addEventListener('change', (e) => {
    const reader = new FileReader();
    reader.onload = (event) => {
        img.src = event.target.result;
        img.onload = () => {
            canvas.width = img.width;
            canvas.height = img.height;
            updateImage();
        };
    };
    reader.readAsDataURL(e.target.files[0]);
});

hueRange.addEventListener('input', updateImage);
bgColor.addEventListener('input', updateBackground);

function updateImage() {
    ctx.clearRect(0, 0, canvas.width, canvas.height);

    // Draw the image in grayscale
    ctx.filter = 'grayscale(100%)';
    ctx.drawImage(img, 0, 0, canvas.width, canvas.height);
    ctx.filter = 'none';

    // Create an offscreen canvas to manipulate the image data
    const offscreenCanvas = document.createElement('canvas');
    offscreenCanvas.width = img.width;
    offscreenCanvas.height = img.height;
    const offscreenCtx = offscreenCanvas.getContext('2d');

    // Draw the grayscale image onto the offscreen canvas
    offscreenCtx.drawImage(img, 0, 0);

    // Get the image data from the offscreen canvas
    const imageData = offscreenCtx.getImageData(0, 0, offscreenCanvas.width, offscreenCanvas.height);
    const data = imageData.data;

    // Iterate through the pixels and adjust the hue
    for (let i = 0; i < data.length; i += 4) {
        const r = data[i];
        const g = data[i + 1];
        const b = data[i + 2];

        const [h, s, l] = rgbToHsl(r, g, b);
        const [newR, newG, newB] = hslToRgb((h + hueRange.value / 360) % 1, s, l);

        data[i] = newR;
        data[i + 1] = newG;
        data[i + 2] = newB;
    }

    // Put the modified image data back onto the offscreen canvas
    offscreenCtx.putImageData(imageData, 0, 0);

    // Draw the colorized image onto the main canvas
    ctx.drawImage(offscreenCanvas, 0, 0, canvas.width, canvas.height);
}

function hslToRgb(h, s, l) {
    let r, g, b;

    if (s === 0) {
        r = g = b = l; // achromatic
    } else {
        const hue2rgb = (p, q, t) => {
            if (t < 0) t += 1;
            if (t > 1) t -= 1;
            if (t < 1 / 6) return p + (q - p) * 6 * t;
            if (t < 1 / 2) return q;
            if (t < 2 / 3) return p + (q - p) * (2 / 3 - t) * 6;
            return p;
        };

        const q = l < 0.5 ? l * (1 + s) : l + s - l * s;
        const p = 2 * l - q;
        r = hue2rgb(p, q, h + 1 / 3);
        g = hue2rgb(p, q, h);
        b = hue2rgb(p, q, h - 1 / 3);
    }

    return [Math.round(r * 255), Math.round(g * 255), Math.round(b * 255)];
}


function rgbToHsl(r, g, b) {
    r /= 255, g /= 255, b /= 255;
    const max = Math.max(r, g, b), min = Math.min(r, g, b);
    let h, s, l = (max + min) / 2;

    if (max === min) {
        h = s = 0; // achromatic
    } else {
        const d = max - min;
        s = l > 0.5 ? d / (2 - max - min) : d / (max + min);
        switch (max) {
            case r: h = (g - b) / d + (g < b ? 6 : 0); break;
            case g: h = (b - r) / d + 2; break;
            case b: h = (r - g) / d + 4; break;
        }
        h /= 6;
    }

    return [h, s, l];
}


function updateBackground() {
    canvas.style.backgroundColor = bgColor.value;
}

## vyvgyyo.markdown

      
    Raw
  

              vyvgyyo.markdown
            
          
    vYVGyyo

A Pen by Jake Brown on CodePen.
License.
	<body>
	<input type="file" id="image-input" accept="image/*">
	<input type="range" id="hue-range" min="0" max="360" value="0">
	<input type="color" id="bg-color" value="#ffffff">
	<canvas id="image-canvas"></canvas>
	<script src="main.js"></script>
	</body>
	const imageInput = document.getElementById('image-input');
	const hueRange = document.getElementById('hue-range');
	const bgColor = document.getElementById('bg-color');
	const canvas = document.getElementById('image-canvas');
	const ctx = canvas.getContext('2d');
	let img = new Image();

	imageInput.addEventListener('change', (e) => {
	const reader = new FileReader();
	reader.onload = (event) => {
	img.src = event.target.result;
	img.onload = () => {
	canvas.width = img.width;
	canvas.height = img.height;
	updateImage();
	};
	};
	reader.readAsDataURL(e.target.files[0]);
	});

	hueRange.addEventListener('input', updateImage);
	bgColor.addEventListener('input', updateBackground);

	function updateImage() {
	ctx.clearRect(0, 0, canvas.width, canvas.height);

	// Draw the image in grayscale
	ctx.filter = 'grayscale(100%)';
	ctx.drawImage(img, 0, 0, canvas.width, canvas.height);
	ctx.filter = 'none';

	// Create an offscreen canvas to manipulate the image data
	const offscreenCanvas = document.createElement('canvas');
	offscreenCanvas.width = img.width;
	offscreenCanvas.height = img.height;
	const offscreenCtx = offscreenCanvas.getContext('2d');

	// Draw the grayscale image onto the offscreen canvas
	offscreenCtx.drawImage(img, 0, 0);

	// Get the image data from the offscreen canvas
	const imageData = offscreenCtx.getImageData(0, 0, offscreenCanvas.width, offscreenCanvas.height);
	const data = imageData.data;

	// Iterate through the pixels and adjust the hue
	for (let i = 0; i < data.length; i += 4) {
	const r = data[i];
	const g = data[i + 1];
	const b = data[i + 2];

	const [h, s, l] = rgbToHsl(r, g, b);
	const [newR, newG, newB] = hslToRgb((h + hueRange.value / 360) % 1, s, l);

	data[i] = newR;
	data[i + 1] = newG;
	data[i + 2] = newB;
	}

	// Put the modified image data back onto the offscreen canvas
	offscreenCtx.putImageData(imageData, 0, 0);

	// Draw the colorized image onto the main canvas
	ctx.drawImage(offscreenCanvas, 0, 0, canvas.width, canvas.height);
	}

	function hslToRgb(h, s, l) {
	let r, g, b;

	if (s === 0) {
	r = g = b = l; // achromatic
	} else {
	const hue2rgb = (p, q, t) => {
	if (t < 0) t += 1;
	if (t > 1) t -= 1;
	if (t < 1 / 6) return p + (q - p) * 6 * t;
	if (t < 1 / 2) return q;
	if (t < 2 / 3) return p + (q - p) * (2 / 3 - t) * 6;
	return p;
	};

	const q = l < 0.5 ? l * (1 + s) : l + s - l * s;
	const p = 2 * l - q;
	r = hue2rgb(p, q, h + 1 / 3);
	g = hue2rgb(p, q, h);
	b = hue2rgb(p, q, h - 1 / 3);
	}

	return [Math.round(r * 255), Math.round(g * 255), Math.round(b * 255)];
	}


	function rgbToHsl(r, g, b) {
	r /= 255, g /= 255, b /= 255;
	const max = Math.max(r, g, b), min = Math.min(r, g, b);
	let h, s, l = (max + min) / 2;

	if (max === min) {
	h = s = 0; // achromatic
	} else {
	const d = max - min;
	s = l > 0.5 ? d / (2 - max - min) : d / (max + min);
	switch (max) {
	case r: h = (g - b) / d + (g < b ? 6 : 0); break;
	case g: h = (b - r) / d + 2; break;
	case b: h = (r - g) / d + 4; break;
	}
	h /= 6;
	}

	return [h, s, l];
	}


	function updateBackground() {
	canvas.style.backgroundColor = bgColor.value;
	}