Basic webp integration (#103)

src/codecs/webp/Encoder.worker.ts

@@ -0,0 +1,80 @@
+import webp_enc from '../../../codecs/webp_enc/webp_enc';
+// Using require() so TypeScript doesn’t complain about this not being a module.
+import { EncodeOptions } from './encoder';
+const wasmBinaryUrl = require('../../../codecs/webp_enc/webp_enc.wasm');
+
+// API exposed by wasm module. Details in the codec’s README.
+interface ModuleAPI {
+  version(): number;
+  create_buffer(width: number, height: number): number;
+  destroy_buffer(pointer: number): void;
+  encode(buffer: number, width: number, height: number, quality: number): void;
+  free_result(): void;
+  get_result_pointer(): number;
+  get_result_size(): number;
+}
+
+export default class WebPEncoder {
+  private emscriptenModule: Promise<EmscriptenWasm.Module>;
+  private api: Promise<ModuleAPI>;
+
+  constructor() {
+    this.emscriptenModule = new Promise((resolve) => {
+      const m = webp_enc({
+        // Just to be safe, don’t automatically invoke any wasm functions
+        noInitialRun: false,
+        locateFile(url: string): string {
+          // Redirect the request for the wasm binary to whatever webpack gave us.
+          if (url.endsWith('.wasm')) {
+            return wasmBinaryUrl;
+          }
+          return url;
+        },
+        onRuntimeInitialized() {
+          // An Emscripten is a then-able that, for some reason, `then()`s itself,
+          // causing an infite loop when you wrap it in a real promise. Deleten the `then`
+          // prop solves this for now.
+          // See: https://github.com/kripken/emscripten/blob/incoming/src/postamble.js#L129
+          // TODO(surma@): File a bug with Emscripten on this.
+          delete (m as any).then;
+          resolve(m);
+        },
+      });
+    });
+
+    this.api = (async () => {
+      // Not sure why, but TypeScript complains that I am using
+      // `emscriptenModule` before it’s getting assigned, which is clearly not
+      // true :shrug: Using `any`
+      const module = await (this as any).emscriptenModule as EmscriptenWasm.Module;
+
+      return {
+        version: module.cwrap('version', 'number', []),
+        create_buffer: module.cwrap('create_buffer', 'number', ['number', 'number']),
+        destroy_buffer: module.cwrap('destroy_buffer', '', ['number']),
+        encode: module.cwrap('encode', '', ['number', 'number', 'number', 'number']),
+        free_result: module.cwrap('free_result', '', []),
+        get_result_pointer: module.cwrap('get_result_pointer', 'number', []),
+        get_result_size: module.cwrap('get_result_size', 'number', []),
+      };
+    })();
+  }
+
+  async encode(data: ImageData, options: EncodeOptions): Promise<ArrayBuffer> {
+    const m = await this.emscriptenModule;
+    const api = await this.api;
+
+    const p = api.create_buffer(data.width, data.height);
+    m.HEAP8.set(data.data, p);
+    api.encode(p, data.width, data.height, options.quality);
+    const resultPointer = api.get_result_pointer();
+    const resultSize = api.get_result_size();
+    const resultView = new Uint8Array(m.HEAP8.buffer, resultPointer, resultSize);
+    const result = new Uint8Array(resultView);
+    api.free_result();
+    api.destroy_buffer(p);
+
+    // wasm can’t run on SharedArrayBuffers, so we hard-cast to ArrayBuffer.
+    return result.buffer as ArrayBuffer;
+  }
+}

src/codecs/webp/encoder.ts

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+import EncoderWorker from './Encoder.worker';
+
+export interface EncodeOptions { quality: number; }
+export interface EncoderState { type: typeof type; options: EncodeOptions; }
+
+export const type = 'webp';
+export const label = 'WebP';
+export const mimeType = 'image/webp';
+export const extension = 'webp';
+export const defaultOptions: EncodeOptions = { quality: 7 };
+
+export async function encode(data: ImageData, options: EncodeOptions) {
+  // We need to await this because it's been comlinked.
+  const encoder = await new EncoderWorker();
+  return encoder.encode(data, options);
+}

src/codecs/webp/options.tsx

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+import qualityOption from '../generic/quality-option';
+
+export default qualityOption();