Typescriptify auto optimizer in libSquoosh

libsquoosh/src/auto-optimizer.ts

@@ -2,6 +2,39 @@ import { instantiateEmscriptenWasm } from './emscripten-utils.js';
 
 import visdif from '../../codecs/visdif/visdif.js';
 import visdifWasm from 'asset-url:../../codecs/visdif/visdif.wasm';
+import type ImageData from './image_data';
+
+interface VisDiff {
+  distance: (data: Uint8ClampedArray) => number;
+  delete: () => void;
+}
+
+interface VisdiffConstructor {
+  new (data: Uint8ClampedArray, width: number, height: number): VisDiff;
+}
+
+interface VisDiffModule extends EmscriptenWasm.Module {
+  VisDiff: VisdiffConstructor;
+}
+
+type VisDiffModuleFactory = EmscriptenWasm.ModuleFactory<VisDiffModule>;
+
+interface BinarySearchParams {
+  min?: number;
+  max?: number;
+  epsilon?: number;
+  maxRounds?: number;
+}
+
+interface AutoOptimizeParams extends BinarySearchParams {
+  butteraugliDistanceGoal?: number;
+}
+
+interface AutoOptimizeResult {
+  bitmap: ImageData;
+  binary: Uint8Array;
+  quality: number;
+}
 
 // `measure` is a (async) function that takes exactly one numeric parameter and
 // returns a value. The function is assumed to be monotonic (an increase in `parameter`
@@ -9,9 +42,9 @@ import visdifWasm from 'asset-url:../../codecs/visdif/visdif.wasm';
 // to find `parameter` such that `measure` returns `measureGoal`, within an error
 // of `epsilon`. It will use at most `maxRounds` attempts.
 export async function binarySearch(
-  measureGoal,
-  measure,
-  { min = 0, max = 100, epsilon = 0.1, maxRounds = 6 } = {},
+  measureGoal: number,
+  measure: (val: number) => Promise<number>,
+  { min = 0, max = 100, epsilon = 0.1, maxRounds = 6 }: BinarySearchParams = {},
 ) {
   let parameter = (max - min) / 2 + min;
   let delta = (max - min) / 4;
@@ -33,12 +66,21 @@ export async function binarySearch(
 }
 
 export async function autoOptimize(
-  bitmapIn,
-  encode,
-  decode,
-  { butteraugliDistanceGoal = 1.4, ...otherOpts } = {},
-) {
-  const { VisDiff } = await instantiateEmscriptenWasm(visdif, visdifWasm);
+  bitmapIn: ImageData,
+  encode: (
+    bitmap: ImageData,
+    quality: number,
+  ) => Promise<Uint8Array> | Uint8Array,
+  decode: (binary: Uint8Array) => Promise<ImageData> | ImageData,
+  {
+    butteraugliDistanceGoal = 1.4,
+    ...binarySearchParams
+  }: AutoOptimizeParams = {},
+): Promise<AutoOptimizeResult> {
+  const { VisDiff } = await instantiateEmscriptenWasm(
+    visdif as VisDiffModuleFactory,
+    visdifWasm,
+  );
 
   const comparator = new VisDiff(
     bitmapIn.data,
@@ -46,8 +88,11 @@ export async function autoOptimize(
     bitmapIn.height,
   );
 
-  let bitmapOut;
-  let binaryOut;
+  // We're able to do non null assertion because
+  // we know that binarySearch will set these values
+  let bitmapOut!: ImageData;
+  let binaryOut!: Uint8Array;
+
   // Increasing quality means _decrease_ in Butteraugli distance.
   // `binarySearch` assumes that increasing `parameter` will
   // increase the metric value. So multipliy Butteraugli values by -1.
@@ -58,7 +103,7 @@ export async function autoOptimize(
       bitmapOut = await decode(binaryOut);
       return -1 * comparator.distance(bitmapOut.data);
     },
-    otherOpts,
+    binarySearchParams,
   );
   comparator.delete();