feat: image knob

package.json

@@ -1,7 +1,7 @@
 {
 	"name": "svelte-knobs",
 	"description": "Svelte component library for building customizable knob controls.",
-	"version": "0.3.0",
+	"version": "0.3.1",
 	"repository": {
 		"url": "https://github.com/eye-wave/svelte-knobs"
 	},

src/lib/ImageKnob.svelte

@@ -0,0 +1,137 @@
+<script lang="ts">
+	import { normalize } from './params.js';
+	import { onMount } from 'svelte';
+	import { spring } from 'svelte/motion';
+	import KnobBase from './KnobBase.svelte';
+	import type { SharedKnobProps } from './KnobBase.svelte';
+
+	type Props = {
+		stiffness?: number;
+		class?: string;
+		source: string;
+		numberOfFrames?: number;
+		width?: number;
+		height?: number;
+	} & SharedKnobProps;
+
+	let {
+		style,
+		source,
+		numberOfFrames = $bindable(),
+		class: className,
+		label = '',
+		unit = '',
+		onChange,
+		value = $bindable(),
+		defaultValue,
+		param,
+		stiffness = 0.5,
+		decimalDigits = 0,
+		snapValues = [],
+		snapThreshold = 0.1,
+		width = 80,
+		height = 80,
+		disabled = false,
+		draggable = true,
+		colors = {}
+	}: Props = $props();
+
+	const rotationDegrees = spring(normalize(value, param) * 270 - 135, { stiffness });
+
+	function draw() {
+		if (!ctx) return;
+		if (!numberOfFrames) return;
+		if (!image) return;
+		if (!('width' in image && 'height' in image)) return;
+
+		const normalized = ($rotationDegrees + 135) / 270;
+		const i = Math.floor(normalized * numberOfFrames);
+		const y = image.width * i;
+
+		if (i < 0) return;
+		if (y >= image.height) return;
+
+		ctx.clearRect(0, 0, canvas.width, canvas.height);
+		ctx.drawImage(
+			image,
+			0, // sx
+			y, // sy
+			image.width, // sWidth
+			image.width, // sHeight
+			0, // dx
+			0, // dy
+			canvas.width, // dWidth
+			canvas.height // dHeight
+		);
+	}
+
+	onMount(() => {
+		ctx = canvas.getContext('2d');
+		ctx?.fillText('Loading...', 0, canvas.height / 2);
+	});
+
+	onMount(() => {
+		if (!source) return;
+
+		console.time('load image');
+
+		image = new Image();
+		image.src = source;
+		image.onload = () => {
+			if (!image) throw Error('What');
+			if (numberOfFrames === undefined) {
+				if ('width' in image && 'height' in image) {
+					console.warn('Automatic estimation of numberOfFrames might be inaccurate');
+					numberOfFrames = Math.floor(image.height / image.width);
+				} else {
+					throw Error('Failed to estimate numberOfFrames');
+				}
+			}
+
+			console.timeEnd('load image');
+			isLoading = false;
+		};
+	});
+
+	$effect(() => {
+		if (isLoading) return;
+		draw();
+	});
+
+	let canvas: HTMLCanvasElement;
+	let ctx: CanvasRenderingContext2D | null = null;
+	let isLoading = $state(true);
+	let image: HTMLImageElement | null = null;
+</script>
+
+<KnobBase
+	{colors}
+	{decimalDigits}
+	{defaultValue}
+	{disabled}
+	{draggable}
+	{label}
+	{onChange}
+	{param}
+	{snapThreshold}
+	{snapValues}
+	{style}
+	{unit}
+	bind:value
+	{rotationDegrees}
+>
+	{#snippet ui({ handleTouchStart, handleMouseDown, handleDblClick })}
+		<canvas
+			bind:this={canvas}
+			{width}
+			{height}
+			class={className}
+			onmousedown={handleMouseDown}
+			ontouchstart={handleTouchStart}
+			ondblclick={handleDblClick}
+			oncontextmenu={(e) => e.preventDefault()}
+			draggable={false}
+		>
+		</canvas>
+	{/snippet}
+</KnobBase>