Add support for PNG decoding (encoding still buggy)

cli/src/codecs.js

@@ -1,5 +1,5 @@
 import { promises as fsp } from "fs";
-import { instantiateEmscriptenWasm } from "./emscripten-utils.js";
+import { instantiateEmscriptenWasm, pathify } from "./emscripten-utils.js";
 
 // MozJPEG
 import mozEnc from "../../codecs/mozjpeg/enc/mozjpeg_enc.js";
@@ -19,6 +19,14 @@ import avifEncWasm from "asset-url:../../codecs/avif/enc/avif_enc.wasm";
 import avifDec from "../../codecs/avif/dec/avif_dec.js";
 import avifDecWasm from "asset-url:../../codecs/avif/dec/avif_dec.wasm";
 
+// PNG
+import pngEncDecInit, {
+  encode as pngEncode,
+  decode as pngDecode
+} from "../../codecs/png/pkg/squoosh_png.js";
+import pngEncDecWasm from "asset-url:../../codecs/png/pkg/squoosh_png_bg.wasm";
+const pngEncDecPromise = pngEncDecInit(fsp.readFile(pathify(pngEncDecWasm)));
+
 // Our decoders currently rely on a `ImageData` global.
 import ImageData from "./image_data.js";
 globalThis.ImageData = ImageData;
@@ -114,5 +122,19 @@ export default {
       min: 0,
       max: 62
     }
+  },
+  png: {
+    name: "PNG",
+    extension: "png",
+    detectors: [/^\x89PNG\x0D\x0A\x1A\x0A/],
+    dec: async () => {
+      await pngEncDecPromise;
+      return { decode: (...args) => pngDecode(...args) };
+    },
+    enc: async () => {
+      await pngEncDecPromise;
+      return { encode: (...args) => new Uint8Array(pngEncode(...args)) };
+    },
+    defaultEncoderOptions: {}
   }
 };

cli/src/emscripten-utils.js

@@ -1,10 +1,13 @@
-export function instantiateEmscriptenWasm(factory, path) {
+export function pathify(path) {
   if (path.startsWith("file://")) {
     path = path.slice("file://".length);
   }
+  return path;
+}
+export function instantiateEmscriptenWasm(factory, path) {
   return factory({
     locateFile() {
-      return path;
+      return pathify(path);
     }
   });
 }

cli/src/image_data.js

@@ -1,6 +1,11 @@
 export default class ImageData {
   constructor(data, width, height) {
-    this.data = data;
+    // Need to manually copy the memory as wasm-bindgen does not by default
+    // and by the time we get control in JS land, the memory has already
+    // been corrupted.
+    // FIXME: This is bad because it’s overhead that we should only need
+    // to pay for Rust, not for C++.
+    this.data = new Uint8ClampedArray(data);
     this.width = width;
     this.height = height;
   }