Load mozjpeg codec and encode image

codecs/mozjpeg_enc/mozjpeg_enc.d.ts

@@ -0,0 +1 @@
+export default function(opts: EmscriptenWasm.ModuleOpts): EmscriptenWasm.Module;

emscripten-wasm.d.ts

@@ -0,0 +1,107 @@
+// These types roughly model the object that the JS files generated by Emscripten define. Copied from https://github.com/DefinitelyTyped/DefinitelyTyped/blob/master/types/emscripten/index.d.ts and turned into a type definition rather than a global to support our way of using Emscripten.
+// TODO(@surma): Upstream this?
+declare namespace EmscriptenWasm {
+  type EnvironmentType = "WEB" | "NODE" | "SHELL" | "WORKER";
+
+  // Options object for modularized Emscripten files. Shoe-horned by @surma.
+  // FIXME: This an incomplete definition!
+  interface ModuleOpts {
+    noInitialRun?: boolean;
+    locateFile?: (url: string) => string;
+    onRuntimeInitialized?: () => void;
+  }
+
+  interface Module {
+    print(str: string): void;
+    printErr(str: string): void;
+    arguments: string[];
+    environment: EnvironmentType;
+    preInit: { ():  void }[];
+    preRun: { ():  void }[];
+    postRun: { ():  void }[];
+    preinitializedWebGLContext: WebGLRenderingContext;
+    noInitialRun: boolean;
+    noExitRuntime: boolean;
+    logReadFiles: boolean;
+    filePackagePrefixURL: string;
+    wasmBinary: ArrayBuffer;
+
+    destroy(object: object): void;
+    getPreloadedPackage(remotePackageName: string, remotePackageSize: number): ArrayBuffer;
+    instantiateWasm(
+        imports: WebAssembly.Imports,
+        successCallback: (module: WebAssembly.Module) => void
+    ): WebAssembly.Exports;
+    locateFile(url: string): string;
+    onCustomMessage(event: MessageEvent): void;
+
+    Runtime: any;
+
+    ccall(ident: string, returnType: string | null, argTypes: string[], args: any[]): any;
+    cwrap(ident: string, returnType: string | null, argTypes: string[]): any;
+
+    setValue(ptr: number, value: any, type: string, noSafe?: boolean): void;
+    getValue(ptr: number, type: string, noSafe?: boolean): number;
+
+    ALLOC_NORMAL: number;
+    ALLOC_STACK: number;
+    ALLOC_STATIC: number;
+    ALLOC_DYNAMIC: number;
+    ALLOC_NONE: number;
+
+    allocate(slab: any, types: string, allocator: number, ptr: number): number;
+    allocate(slab: any, types: string[], allocator: number, ptr: number): number;
+
+    Pointer_stringify(ptr: number, length?: number): string;
+    UTF16ToString(ptr: number): string;
+    stringToUTF16(str: string, outPtr: number): void;
+    UTF32ToString(ptr: number): string;
+    stringToUTF32(str: string, outPtr: number): void;
+
+    // USE_TYPED_ARRAYS == 1
+    HEAP: Int32Array;
+    IHEAP: Int32Array;
+    FHEAP: Float64Array;
+
+    // USE_TYPED_ARRAYS == 2
+    HEAP8: Int8Array;
+    HEAP16: Int16Array;
+    HEAP32: Int32Array;
+    HEAPU8:  Uint8Array;
+    HEAPU16: Uint16Array;
+    HEAPU32: Uint32Array;
+    HEAPF32: Float32Array;
+    HEAPF64: Float64Array;
+
+    TOTAL_STACK: number;
+    TOTAL_MEMORY: number;
+    FAST_MEMORY: number;
+
+    addOnPreRun(cb: () => any): void;
+    addOnInit(cb: () => any): void;
+    addOnPreMain(cb: () => any): void;
+    addOnExit(cb: () => any): void;
+    addOnPostRun(cb: () => any): void;
+
+    // Tools
+    intArrayFromString(stringy: string, dontAddNull?: boolean, length?: number): number[];
+    intArrayToString(array: number[]): string;
+    writeStringToMemory(str: string, buffer: number, dontAddNull: boolean): void;
+    writeArrayToMemory(array: number[], buffer: number): void;
+    writeAsciiToMemory(str: string, buffer: number, dontAddNull: boolean): void;
+
+    addRunDependency(id: any): void;
+    removeRunDependency(id: any): void;
+
+
+    preloadedImages: any;
+    preloadedAudios: any;
+
+    _malloc(size: number): number;
+    _free(ptr: number): void;
+
+    // Augmentations below by @surma.
+    onRuntimeInitialized: () => void | null;
+  }
+}
+

package.json

@@ -4,6 +4,8 @@
   "version": "0.0.0",
   "license": "apache-2.0",
   "scripts": {
+    "build:mozjpeg_enc": "cd codecs/mozjpeg_enc && npm run build",
+    "build:codecs": "npm run build:mozjpeg_enc",
     "start": "webpack serve --hot",
     "build": "webpack -p",
     "lint": "eslint src"
@@ -30,6 +32,7 @@
   ],
   "devDependencies": {
     "@types/node": "^9.4.7",
+    "@types/webassembly-js-api": "0.0.1",
     "babel-loader": "^7.1.4",
     "babel-plugin-jsx-pragmatic": "^1.0.2",
     "babel-plugin-syntax-dynamic-import": "^6.18.0",
@@ -52,6 +55,8 @@
     "eslint-plugin-promise": "^3.7.0",
     "eslint-plugin-react": "^7.7.0",
     "eslint-plugin-standard": "^3.0.1",
+    "exports-loader": "^0.7.0",
+    "file-loader": "^1.1.11",
     "html-webpack-plugin": "^3.0.6",
     "if-env": "^1.0.4",
     "loader-utils": "^1.1.0",

src/components/app/index.tsx

@@ -1,8 +1,10 @@
 import { h, Component } from 'preact';
-import { bind } from '../../lib/util';
+import { bind, bitmapToImageData } from '../../lib/util';
 import * as style from './style.scss';
 import Output from '../output';
 
+import {MozJpegEncoder} from '../../lib/codec-wrappers/mozjpeg-enc';
+
 type Props = {};
 
 type State = {
@@ -28,8 +30,13 @@ export default class App extends Component<Props, State> {
     const fileInput = event.target as HTMLInputElement;
     if (!fileInput.files || !fileInput.files[0]) return;
     // TODO: handle decode error
-    const img = await createImageBitmap(fileInput.files[0]);
-    this.setState({ img });
+    const bitmap = await createImageBitmap(fileInput.files[0]);
+    const data = await bitmapToImageData(bitmap);
+    const encoder = new MozJpegEncoder();
+    const compressedData = await encoder.encode(data);
+    const blob = new Blob([compressedData], {type: 'image/jpeg'});
+    const compressedImage = await createImageBitmap(blob);
+    this.setState({ img: compressedImage });
   }
 
   render({ }: Props, { img }: State) {
@@ -47,3 +54,4 @@ export default class App extends Component<Props, State> {
     );
   }
 }
+

src/lib/codec-wrappers/codec.ts

@@ -0,0 +1,7 @@
+export interface Encoder {
+  encode(data: ImageData): Promise<ArrayBuffer>;
+}
+
+export interface Decoder {
+  decode(data: ArrayBuffer): Promise<ImageBitmap>;
+}

src/lib/codec-wrappers/mozjpeg-enc.ts

@@ -0,0 +1,76 @@
+import {Encoder} from './codec';
+
+import mozjpeg_enc from '../../../codecs/mozjpeg_enc/mozjpeg_enc';
+// Using require() so TypeScript doesn’t complain about this not being a module.
+const wasmBinaryUrl = require('../../../codecs/mozjpeg_enc/mozjpeg_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 class MozJpegEncoder implements Encoder {
+  private emscriptenModule: Promise<EmscriptenWasm.Module>;
+  private api: Promise<ModuleAPI>;
+  constructor() {
+    this.emscriptenModule = new Promise(resolve => {
+      const m = mozjpeg_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 m = await (this as any).emscriptenModule;
+      return {
+        version: m.cwrap('version', 'number', []),
+        create_buffer: m.cwrap('create_buffer', 'number', ['number', 'number']),
+        destroy_buffer: m.cwrap('destroy_buffer', '', ['number']),
+        encode: m.cwrap('encode', '', ['number', 'number', 'number', 'number']),
+        free_result: m.cwrap('free_result', '', []),
+        get_result_pointer: m.cwrap('get_result_pointer', 'number', []),
+        get_result_size: m.cwrap('get_result_size', 'number', []),
+      };
+    })();
+  }
+
+  async encode(data: ImageData): Promise<ArrayBuffer | SharedArrayBuffer> {
+    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, 2);
+    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);
+
+    return result.buffer;
+  }
+}

src/lib/util.ts

@@ -24,3 +24,22 @@ export function bind(target: any, propertyKey: string, descriptor: PropertyDescr
     }
   };
 }
+
+/**
+ * Turns a given `ImageBitmap` into `ImageData`.
+ */
+export async function bitmapToImageData(bitmap: ImageBitmap): Promise<ImageData> {
+  // Make canvas same size as image
+  // TODO: Move this off-thread if possible with `OffscreenCanvas` or iFrames?
+  const canvas = document.createElement('canvas');
+  canvas.width = bitmap.width;
+  canvas.height = bitmap.height;
+  // Draw image onto canvas
+  const ctx = canvas.getContext('2d');
+  if (!ctx) {
+    throw new Error("Could not create canvas context");
+  }
+  ctx.drawImage(bitmap, 0, 0);
+  return ctx.getImageData(0, 0, bitmap.width, bitmap.height);
+}
+

webpack.config.js

@@ -107,10 +107,23 @@ module.exports = function (_, env) {
           loader: 'babel-loader',
           // Don't respect any Babel RC files found on the filesystem:
           options: Object.assign(readJson('.babelrc'), { babelrc: false })
+        },
+        {
+          // All the codec files define a global with the same name as their file name. `exports-loader` attaches those to `module.exports`.
+          test: /\/codecs\/.*\.js$/,
+          loader: 'exports-loader',
+        },
+        {
+          test: /\/codecs\/.*\.wasm$/,
+          // This is needed to make webpack NOT process wasm files.
+          // See https://github.com/webpack/webpack/issues/6725
+          type: 'javascript/auto',
+          loader: 'file-loader',
         }
-      ]
+      ],
     },
     plugins: [
+      new webpack.IgnorePlugin(/(fs)/, /\/codecs\//),
       // Pretty progressbar showing build progress:
       new ProgressBarPlugin({
         format: '\u001b[90m\u001b[44mBuild\u001b[49m\u001b[39m [:bar] \u001b[32m\u001b[1m:percent\u001b[22m\u001b[39m (:elapseds) \u001b[2m:msg\u001b[22m\r',