1 files changed, 194 insertions, 0 deletions
diff --git a/apps/web/src/services/renderer/effect-preview.ts b/apps/web/src/services/renderer/effect-preview.ts
new file mode 100644
index 00000000..2cebec5d
--- /dev/null
+++ b/apps/web/src/services/renderer/effect-preview.ts
@@ -0,0 +1,194 @@
+import { createOffscreenCanvas } from "./canvas-utils";
+import { getEffect } from "@/lib/effects";
+import type { EffectParamValues } from "@/types/effects";
+import { applyMultiPassEffect } from "./webgl-utils";
+import type { EffectPassData } from "./webgl-utils";
+
+const PREVIEW_SIZE = 160;
+const PREVIEW_IMAGE_PATH = "/effects/preview.jpg";
+
+let previewGl: WebGLRenderingContext | null = null;
+let previewCanvas: OffscreenCanvas | HTMLCanvasElement | null = null;
+let testSourceCanvas: OffscreenCanvas | HTMLCanvasElement | null = null;
+let previewImageElement: HTMLImageElement | null = null;
+const programCache = new Map<string, WebGLProgram>();
+const onReadyCallbacks = new Set<() => void>();
+
+export function onPreviewImageReady({
+	callback,
+}: {
+	callback: () => void;
+}): () => void {
+	onReadyCallbacks.add(callback);
+	return () => onReadyCallbacks.delete(callback);
+}
+
+function loadPreviewImage(): void {
+	if (typeof window === "undefined") return;
+	const image = new Image();
+	image.onload = () => {
+		testSourceCanvas = null;
+		for (const callback of onReadyCallbacks) {
+			callback();
+		}
+	};
+	image.src = PREVIEW_IMAGE_PATH;
+	previewImageElement = image;
+}
+
+loadPreviewImage();
+
+function buildDefaultParams({
+	effectType,
+}: {
+	effectType: string;
+}): EffectParamValues {
+	const definition = getEffect({ effectType });
+	const params: EffectParamValues = {};
+	for (const paramDef of definition.params) {
+		params[paramDef.key] = paramDef.default;
+	}
+	return params;
+}
+
+function createTestSource({
+	width,
+	height,
+}: {
+	width: number;
+	height: number;
+}): OffscreenCanvas | HTMLCanvasElement | null {
+	const isImageReady =
+		previewImageElement?.complete &&
+		(previewImageElement.naturalWidth ?? 0) > 0;
+	if (!isImageReady || !previewImageElement) {
+		return null;
+	}
+
+	const canvas = createOffscreenCanvas({ width, height });
+	const ctx = canvas.getContext("2d") as
+		| CanvasRenderingContext2D
+		| OffscreenCanvasRenderingContext2D
+		| null;
+	if (!ctx) {
+		throw new Error("failed to get 2d context for test source");
+	}
+	ctx.drawImage(previewImageElement, 0, 0, width, height);
+	return canvas;
+}
+
+function getOrCreatePreviewContext({
+	width,
+	height,
+}: {
+	width: number;
+	height: number;
+}): { canvas: OffscreenCanvas | HTMLCanvasElement; gl: WebGLRenderingContext } {
+	if (!previewCanvas || !previewGl) {
+		previewCanvas = createOffscreenCanvas({ width, height });
+		previewGl = previewCanvas.getContext("webgl", {
+			premultipliedAlpha: false,
+		}) as WebGLRenderingContext | null;
+		if (!previewGl) {
+			throw new Error("WebGL not supported");
+		}
+	}
+	if (previewCanvas.width !== width || previewCanvas.height !== height) {
+		previewCanvas.width = width;
+		previewCanvas.height = height;
+	}
+	return { canvas: previewCanvas, gl: previewGl };
+}
+
+function getTestSource({
+	width,
+	height,
+}: {
+	width: number;
+	height: number;
+}): CanvasImageSource | null {
+	if (
+		!testSourceCanvas ||
+		testSourceCanvas.width !== width ||
+		testSourceCanvas.height !== height
+	) {
+		testSourceCanvas = createTestSource({ width, height });
+	}
+	return testSourceCanvas;
+}
+
+function applyWebGlEffect({
+	source,
+	width,
+	height,
+	passes,
+}: {
+	source: CanvasImageSource;
+	width: number;
+	height: number;
+	passes: EffectPassData[];
+}): OffscreenCanvas | HTMLCanvasElement {
+	const { canvas: glCanvas, gl } = getOrCreatePreviewContext({ width, height });
+
+	applyMultiPassEffect({ context: gl, source, width, height, passes, programCache });
+
+	const outputCanvas = createOffscreenCanvas({ width, height });
+	const outputCtx = outputCanvas.getContext("2d") as
+		| CanvasRenderingContext2D
+		| OffscreenCanvasRenderingContext2D
+		| null;
+	if (outputCtx) {
+		outputCtx.drawImage(glCanvas, 0, 0, width, height);
+	}
+	return outputCanvas;
+}
+
+export function renderPreview({
+	effectType,
+	params,
+	targetCanvas,
+}: {
+	effectType: string;
+	params: EffectParamValues;
+	targetCanvas: HTMLCanvasElement;
+}): void {
+	const size = PREVIEW_SIZE;
+	const source = getTestSource({ width: size, height: size });
+	if (!source) return;
+
+	const definition = getEffect({ effectType });
+	const resolvedParams =
+		Object.keys(params).length > 0
+			? params
+			: buildDefaultParams({ effectType });
+
+	const passes = definition.renderer.passes.map((pass) => ({
+		fragmentShader: pass.fragmentShader,
+		uniforms: pass.uniforms({
+			effectParams: resolvedParams,
+			width: size,
+			height: size,
+		}),
+	}));
+	const result = applyWebGlEffect({
+		source,
+		width: size,
+		height: size,
+		passes,
+	});
+
+	const targetCtx = targetCanvas.getContext(
+		"2d",
+	) as CanvasRenderingContext2D | null;
+	if (targetCtx) {
+		targetCanvas.width = size;
+		targetCanvas.height = size;
+		targetCtx.drawImage(result, 0, 0, size, size);
+	}
+}
+
+export const effectPreviewService = {
+	renderPreview,
+	onPreviewImageReady,
+	PREVIEW_SIZE,
+};