+ Go+Wasm image dithering tool
+ Featuring the Nord Color Palette
+
+ Load an image, click Go and wait (potentially for a while) for the image
+ to be dithered using the Nord color palette and the Floyd-Steinberg
+ algorithm.
+
+
+ Performance isn't great, as Go+Wasm only runs on a single thread. The
+ Wasm call also blocks the rendering (that would be fixable, though).
+
+
+ If you're into that sort of thing, source code is available on
+ GitHub .
+
+
+
+
+
+
+
diff --git a/dist/main.js b/dist/main.js
new file mode 100644
index 0000000..341f03f
--- /dev/null
+++ b/dist/main.js
@@ -0,0 +1,38 @@
+(async () => {
+ // Load element references
+ const fileInput = document.getElementById("source-image");
+ const btn = document.getElementById("go-btn");
+
+ // Setup Wasm stuff
+ const go = new Go();
+ vm = await WebAssembly.instantiateStreaming(
+ fetch("/main.wasm"),
+ go.importObject
+ );
+ go.run(vm.instance);
+
+ // Setup event listener
+ btn.addEventListener("click", async () => {
+ // Clear image
+ outputElement = document.getElementById("output");
+ outputElement.src = "";
+
+ // Check if a file was selected
+ if (fileInput.files.length === 0) {
+ alert("No file selected");
+ return;
+ }
+ reader = new FileReader();
+ reader.readAsArrayBuffer(fileInput.files[0]);
+ reader.Read;
+ reader.onloadend = async (evt) => {
+ if (evt.target.readyState === FileReader.DONE) {
+ const array = new Uint8Array(evt.target.result);
+ // Wasm magic happens here
+ ditheredImageData = await DitherNord(array);
+ document.getElementById("output").src =
+ "data:image/png;base64," + ditheredImageData;
+ }
+ };
+ });
+})();
diff --git a/dist/main.wasm b/dist/main.wasm
new file mode 100755
index 0000000..dd5d917
Binary files /dev/null and b/dist/main.wasm differ
diff --git a/dist/wasm_exec.js b/dist/wasm_exec.js
new file mode 100644
index 0000000..5651141
--- /dev/null
+++ b/dist/wasm_exec.js
@@ -0,0 +1,636 @@
+// Copyright 2018 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+(() => {
+ // Map multiple JavaScript environments to a single common API,
+ // preferring web standards over Node.js API.
+ //
+ // Environments considered:
+ // - Browsers
+ // - Node.js
+ // - Electron
+ // - Parcel
+ // - Webpack
+
+ if (typeof global !== "undefined") {
+ // global already exists
+ } else if (typeof window !== "undefined") {
+ window.global = window;
+ } else if (typeof self !== "undefined") {
+ self.global = self;
+ } else {
+ throw new Error("cannot export Go (neither global, window nor self is defined)");
+ }
+
+ if (!global.require && typeof require !== "undefined") {
+ global.require = require;
+ }
+
+ if (!global.fs && global.require) {
+ const fs = require("fs");
+ if (typeof fs === "object" && fs !== null && Object.keys(fs).length !== 0) {
+ global.fs = fs;
+ }
+ }
+
+ const enosys = () => {
+ const err = new Error("not implemented");
+ err.code = "ENOSYS";
+ return err;
+ };
+
+ if (!global.fs) {
+ let outputBuf = "";
+ global.fs = {
+ constants: { O_WRONLY: -1, O_RDWR: -1, O_CREAT: -1, O_TRUNC: -1, O_APPEND: -1, O_EXCL: -1 }, // unused
+ writeSync(fd, buf) {
+ outputBuf += decoder.decode(buf);
+ const nl = outputBuf.lastIndexOf("\n");
+ if (nl != -1) {
+ console.log(outputBuf.substr(0, nl));
+ outputBuf = outputBuf.substr(nl + 1);
+ }
+ return buf.length;
+ },
+ write(fd, buf, offset, length, position, callback) {
+ if (offset !== 0 || length !== buf.length || position !== null) {
+ callback(enosys());
+ return;
+ }
+ const n = this.writeSync(fd, buf);
+ callback(null, n);
+ },
+ chmod(path, mode, callback) { callback(enosys()); },
+ chown(path, uid, gid, callback) { callback(enosys()); },
+ close(fd, callback) { callback(enosys()); },
+ fchmod(fd, mode, callback) { callback(enosys()); },
+ fchown(fd, uid, gid, callback) { callback(enosys()); },
+ fstat(fd, callback) { callback(enosys()); },
+ fsync(fd, callback) { callback(null); },
+ ftruncate(fd, length, callback) { callback(enosys()); },
+ lchown(path, uid, gid, callback) { callback(enosys()); },
+ link(path, link, callback) { callback(enosys()); },
+ lstat(path, callback) { callback(enosys()); },
+ mkdir(path, perm, callback) { callback(enosys()); },
+ open(path, flags, mode, callback) { callback(enosys()); },
+ read(fd, buffer, offset, length, position, callback) { callback(enosys()); },
+ readdir(path, callback) { callback(enosys()); },
+ readlink(path, callback) { callback(enosys()); },
+ rename(from, to, callback) { callback(enosys()); },
+ rmdir(path, callback) { callback(enosys()); },
+ stat(path, callback) { callback(enosys()); },
+ symlink(path, link, callback) { callback(enosys()); },
+ truncate(path, length, callback) { callback(enosys()); },
+ unlink(path, callback) { callback(enosys()); },
+ utimes(path, atime, mtime, callback) { callback(enosys()); },
+ };
+ }
+
+ if (!global.process) {
+ global.process = {
+ getuid() { return -1; },
+ getgid() { return -1; },
+ geteuid() { return -1; },
+ getegid() { return -1; },
+ getgroups() { throw enosys(); },
+ pid: -1,
+ ppid: -1,
+ umask() { throw enosys(); },
+ cwd() { throw enosys(); },
+ chdir() { throw enosys(); },
+ }
+ }
+
+ if (!global.crypto && global.require) {
+ const nodeCrypto = require("crypto");
+ global.crypto = {
+ getRandomValues(b) {
+ nodeCrypto.randomFillSync(b);
+ },
+ };
+ }
+ if (!global.crypto) {
+ throw new Error("global.crypto is not available, polyfill required (getRandomValues only)");
+ }
+
+ if (!global.performance) {
+ global.performance = {
+ now() {
+ const [sec, nsec] = process.hrtime();
+ return sec * 1000 + nsec / 1000000;
+ },
+ };
+ }
+
+ if (!global.TextEncoder && global.require) {
+ global.TextEncoder = require("util").TextEncoder;
+ }
+ if (!global.TextEncoder) {
+ throw new Error("global.TextEncoder is not available, polyfill required");
+ }
+
+ if (!global.TextDecoder && global.require) {
+ global.TextDecoder = require("util").TextDecoder;
+ }
+ if (!global.TextDecoder) {
+ throw new Error("global.TextDecoder is not available, polyfill required");
+ }
+
+ // End of polyfills for common API.
+
+ const encoder = new TextEncoder("utf-8");
+ const decoder = new TextDecoder("utf-8");
+
+ global.Go = class {
+ constructor() {
+ this.argv = ["js"];
+ this.env = {};
+ this.exit = (code) => {
+ if (code !== 0) {
+ console.warn("exit code:", code);
+ }
+ };
+ this._exitPromise = new Promise((resolve) => {
+ this._resolveExitPromise = resolve;
+ });
+ this._pendingEvent = null;
+ this._scheduledTimeouts = new Map();
+ this._nextCallbackTimeoutID = 1;
+
+ const setInt64 = (addr, v) => {
+ this.mem.setUint32(addr + 0, v, true);
+ this.mem.setUint32(addr + 4, Math.floor(v / 4294967296), true);
+ }
+
+ const getInt64 = (addr) => {
+ const low = this.mem.getUint32(addr + 0, true);
+ const high = this.mem.getInt32(addr + 4, true);
+ return low + high * 4294967296;
+ }
+
+ const loadValue = (addr) => {
+ const f = this.mem.getFloat64(addr, true);
+ if (f === 0) {
+ return undefined;
+ }
+ if (!isNaN(f)) {
+ return f;
+ }
+
+ const id = this.mem.getUint32(addr, true);
+ return this._values[id];
+ }
+
+ const storeValue = (addr, v) => {
+ const nanHead = 0x7FF80000;
+
+ if (typeof v === "number" && v !== 0) {
+ if (isNaN(v)) {
+ this.mem.setUint32(addr + 4, nanHead, true);
+ this.mem.setUint32(addr, 0, true);
+ return;
+ }
+ this.mem.setFloat64(addr, v, true);
+ return;
+ }
+
+ if (v === undefined) {
+ this.mem.setFloat64(addr, 0, true);
+ return;
+ }
+
+ let id = this._ids.get(v);
+ if (id === undefined) {
+ id = this._idPool.pop();
+ if (id === undefined) {
+ id = this._values.length;
+ }
+ this._values[id] = v;
+ this._goRefCounts[id] = 0;
+ this._ids.set(v, id);
+ }
+ this._goRefCounts[id]++;
+ let typeFlag = 0;
+ switch (typeof v) {
+ case "object":
+ if (v !== null) {
+ typeFlag = 1;
+ }
+ break;
+ case "string":
+ typeFlag = 2;
+ break;
+ case "symbol":
+ typeFlag = 3;
+ break;
+ case "function":
+ typeFlag = 4;
+ break;
+ }
+ this.mem.setUint32(addr + 4, nanHead | typeFlag, true);
+ this.mem.setUint32(addr, id, true);
+ }
+
+ const loadSlice = (addr) => {
+ const array = getInt64(addr + 0);
+ const len = getInt64(addr + 8);
+ return new Uint8Array(this._inst.exports.mem.buffer, array, len);
+ }
+
+ const loadSliceOfValues = (addr) => {
+ const array = getInt64(addr + 0);
+ const len = getInt64(addr + 8);
+ const a = new Array(len);
+ for (let i = 0; i < len; i++) {
+ a[i] = loadValue(array + i * 8);
+ }
+ return a;
+ }
+
+ const loadString = (addr) => {
+ const saddr = getInt64(addr + 0);
+ const len = getInt64(addr + 8);
+ return decoder.decode(new DataView(this._inst.exports.mem.buffer, saddr, len));
+ }
+
+ const timeOrigin = Date.now() - performance.now();
+ this.importObject = {
+ go: {
+ // Go's SP does not change as long as no Go code is running. Some operations (e.g. calls, getters and setters)
+ // may synchronously trigger a Go event handler. This makes Go code get executed in the middle of the imported
+ // function. A goroutine can switch to a new stack if the current stack is too small (see morestack function).
+ // This changes the SP, thus we have to update the SP used by the imported function.
+
+ // func wasmExit(code int32)
+ "runtime.wasmExit": (sp) => {
+ sp >>>= 0;
+ const code = this.mem.getInt32(sp + 8, true);
+ this.exited = true;
+ delete this._inst;
+ delete this._values;
+ delete this._goRefCounts;
+ delete this._ids;
+ delete this._idPool;
+ this.exit(code);
+ },
+
+ // func wasmWrite(fd uintptr, p unsafe.Pointer, n int32)
+ "runtime.wasmWrite": (sp) => {
+ sp >>>= 0;
+ const fd = getInt64(sp + 8);
+ const p = getInt64(sp + 16);
+ const n = this.mem.getInt32(sp + 24, true);
+ fs.writeSync(fd, new Uint8Array(this._inst.exports.mem.buffer, p, n));
+ },
+
+ // func resetMemoryDataView()
+ "runtime.resetMemoryDataView": (sp) => {
+ sp >>>= 0;
+ this.mem = new DataView(this._inst.exports.mem.buffer);
+ },
+
+ // func nanotime1() int64
+ "runtime.nanotime1": (sp) => {
+ sp >>>= 0;
+ setInt64(sp + 8, (timeOrigin + performance.now()) * 1000000);
+ },
+
+ // func walltime() (sec int64, nsec int32)
+ "runtime.walltime": (sp) => {
+ sp >>>= 0;
+ const msec = (new Date).getTime();
+ setInt64(sp + 8, msec / 1000);
+ this.mem.setInt32(sp + 16, (msec % 1000) * 1000000, true);
+ },
+
+ // func scheduleTimeoutEvent(delay int64) int32
+ "runtime.scheduleTimeoutEvent": (sp) => {
+ sp >>>= 0;
+ const id = this._nextCallbackTimeoutID;
+ this._nextCallbackTimeoutID++;
+ this._scheduledTimeouts.set(id, setTimeout(
+ () => {
+ this._resume();
+ while (this._scheduledTimeouts.has(id)) {
+ // for some reason Go failed to register the timeout event, log and try again
+ // (temporary workaround for https://github.com/golang/go/issues/28975)
+ console.warn("scheduleTimeoutEvent: missed timeout event");
+ this._resume();
+ }
+ },
+ getInt64(sp + 8) + 1, // setTimeout has been seen to fire up to 1 millisecond early
+ ));
+ this.mem.setInt32(sp + 16, id, true);
+ },
+
+ // func clearTimeoutEvent(id int32)
+ "runtime.clearTimeoutEvent": (sp) => {
+ sp >>>= 0;
+ const id = this.mem.getInt32(sp + 8, true);
+ clearTimeout(this._scheduledTimeouts.get(id));
+ this._scheduledTimeouts.delete(id);
+ },
+
+ // func getRandomData(r []byte)
+ "runtime.getRandomData": (sp) => {
+ sp >>>= 0;
+ crypto.getRandomValues(loadSlice(sp + 8));
+ },
+
+ // func finalizeRef(v ref)
+ "syscall/js.finalizeRef": (sp) => {
+ sp >>>= 0;
+ const id = this.mem.getUint32(sp + 8, true);
+ this._goRefCounts[id]--;
+ if (this._goRefCounts[id] === 0) {
+ const v = this._values[id];
+ this._values[id] = null;
+ this._ids.delete(v);
+ this._idPool.push(id);
+ }
+ },
+
+ // func stringVal(value string) ref
+ "syscall/js.stringVal": (sp) => {
+ sp >>>= 0;
+ storeValue(sp + 24, loadString(sp + 8));
+ },
+
+ // func valueGet(v ref, p string) ref
+ "syscall/js.valueGet": (sp) => {
+ sp >>>= 0;
+ const result = Reflect.get(loadValue(sp + 8), loadString(sp + 16));
+ sp = this._inst.exports.getsp() >>> 0; // see comment above
+ storeValue(sp + 32, result);
+ },
+
+ // func valueSet(v ref, p string, x ref)
+ "syscall/js.valueSet": (sp) => {
+ sp >>>= 0;
+ Reflect.set(loadValue(sp + 8), loadString(sp + 16), loadValue(sp + 32));
+ },
+
+ // func valueDelete(v ref, p string)
+ "syscall/js.valueDelete": (sp) => {
+ sp >>>= 0;
+ Reflect.deleteProperty(loadValue(sp + 8), loadString(sp + 16));
+ },
+
+ // func valueIndex(v ref, i int) ref
+ "syscall/js.valueIndex": (sp) => {
+ sp >>>= 0;
+ storeValue(sp + 24, Reflect.get(loadValue(sp + 8), getInt64(sp + 16)));
+ },
+
+ // valueSetIndex(v ref, i int, x ref)
+ "syscall/js.valueSetIndex": (sp) => {
+ sp >>>= 0;
+ Reflect.set(loadValue(sp + 8), getInt64(sp + 16), loadValue(sp + 24));
+ },
+
+ // func valueCall(v ref, m string, args []ref) (ref, bool)
+ "syscall/js.valueCall": (sp) => {
+ sp >>>= 0;
+ try {
+ const v = loadValue(sp + 8);
+ const m = Reflect.get(v, loadString(sp + 16));
+ const args = loadSliceOfValues(sp + 32);
+ const result = Reflect.apply(m, v, args);
+ sp = this._inst.exports.getsp() >>> 0; // see comment above
+ storeValue(sp + 56, result);
+ this.mem.setUint8(sp + 64, 1);
+ } catch (err) {
+ sp = this._inst.exports.getsp() >>> 0; // see comment above
+ storeValue(sp + 56, err);
+ this.mem.setUint8(sp + 64, 0);
+ }
+ },
+
+ // func valueInvoke(v ref, args []ref) (ref, bool)
+ "syscall/js.valueInvoke": (sp) => {
+ sp >>>= 0;
+ try {
+ const v = loadValue(sp + 8);
+ const args = loadSliceOfValues(sp + 16);
+ const result = Reflect.apply(v, undefined, args);
+ sp = this._inst.exports.getsp() >>> 0; // see comment above
+ storeValue(sp + 40, result);
+ this.mem.setUint8(sp + 48, 1);
+ } catch (err) {
+ sp = this._inst.exports.getsp() >>> 0; // see comment above
+ storeValue(sp + 40, err);
+ this.mem.setUint8(sp + 48, 0);
+ }
+ },
+
+ // func valueNew(v ref, args []ref) (ref, bool)
+ "syscall/js.valueNew": (sp) => {
+ sp >>>= 0;
+ try {
+ const v = loadValue(sp + 8);
+ const args = loadSliceOfValues(sp + 16);
+ const result = Reflect.construct(v, args);
+ sp = this._inst.exports.getsp() >>> 0; // see comment above
+ storeValue(sp + 40, result);
+ this.mem.setUint8(sp + 48, 1);
+ } catch (err) {
+ sp = this._inst.exports.getsp() >>> 0; // see comment above
+ storeValue(sp + 40, err);
+ this.mem.setUint8(sp + 48, 0);
+ }
+ },
+
+ // func valueLength(v ref) int
+ "syscall/js.valueLength": (sp) => {
+ sp >>>= 0;
+ setInt64(sp + 16, parseInt(loadValue(sp + 8).length));
+ },
+
+ // valuePrepareString(v ref) (ref, int)
+ "syscall/js.valuePrepareString": (sp) => {
+ sp >>>= 0;
+ const str = encoder.encode(String(loadValue(sp + 8)));
+ storeValue(sp + 16, str);
+ setInt64(sp + 24, str.length);
+ },
+
+ // valueLoadString(v ref, b []byte)
+ "syscall/js.valueLoadString": (sp) => {
+ sp >>>= 0;
+ const str = loadValue(sp + 8);
+ loadSlice(sp + 16).set(str);
+ },
+
+ // func valueInstanceOf(v ref, t ref) bool
+ "syscall/js.valueInstanceOf": (sp) => {
+ sp >>>= 0;
+ this.mem.setUint8(sp + 24, (loadValue(sp + 8) instanceof loadValue(sp + 16)) ? 1 : 0);
+ },
+
+ // func copyBytesToGo(dst []byte, src ref) (int, bool)
+ "syscall/js.copyBytesToGo": (sp) => {
+ sp >>>= 0;
+ const dst = loadSlice(sp + 8);
+ const src = loadValue(sp + 32);
+ if (!(src instanceof Uint8Array || src instanceof Uint8ClampedArray)) {
+ this.mem.setUint8(sp + 48, 0);
+ return;
+ }
+ const toCopy = src.subarray(0, dst.length);
+ dst.set(toCopy);
+ setInt64(sp + 40, toCopy.length);
+ this.mem.setUint8(sp + 48, 1);
+ },
+
+ // func copyBytesToJS(dst ref, src []byte) (int, bool)
+ "syscall/js.copyBytesToJS": (sp) => {
+ sp >>>= 0;
+ const dst = loadValue(sp + 8);
+ const src = loadSlice(sp + 16);
+ if (!(dst instanceof Uint8Array || dst instanceof Uint8ClampedArray)) {
+ this.mem.setUint8(sp + 48, 0);
+ return;
+ }
+ const toCopy = src.subarray(0, dst.length);
+ dst.set(toCopy);
+ setInt64(sp + 40, toCopy.length);
+ this.mem.setUint8(sp + 48, 1);
+ },
+
+ "debug": (value) => {
+ console.log(value);
+ },
+ }
+ };
+ }
+
+ async run(instance) {
+ if (!(instance instanceof WebAssembly.Instance)) {
+ throw new Error("Go.run: WebAssembly.Instance expected");
+ }
+ this._inst = instance;
+ this.mem = new DataView(this._inst.exports.mem.buffer);
+ this._values = [ // JS values that Go currently has references to, indexed by reference id
+ NaN,
+ 0,
+ null,
+ true,
+ false,
+ global,
+ this,
+ ];
+ this._goRefCounts = new Array(this._values.length).fill(Infinity); // number of references that Go has to a JS value, indexed by reference id
+ this._ids = new Map([ // mapping from JS values to reference ids
+ [0, 1],
+ [null, 2],
+ [true, 3],
+ [false, 4],
+ [global, 5],
+ [this, 6],
+ ]);
+ this._idPool = []; // unused ids that have been garbage collected
+ this.exited = false; // whether the Go program has exited
+
+ // Pass command line arguments and environment variables to WebAssembly by writing them to the linear memory.
+ let offset = 4096;
+
+ const strPtr = (str) => {
+ const ptr = offset;
+ const bytes = encoder.encode(str + "\0");
+ new Uint8Array(this.mem.buffer, offset, bytes.length).set(bytes);
+ offset += bytes.length;
+ if (offset % 8 !== 0) {
+ offset += 8 - (offset % 8);
+ }
+ return ptr;
+ };
+
+ const argc = this.argv.length;
+
+ const argvPtrs = [];
+ this.argv.forEach((arg) => {
+ argvPtrs.push(strPtr(arg));
+ });
+ argvPtrs.push(0);
+
+ const keys = Object.keys(this.env).sort();
+ keys.forEach((key) => {
+ argvPtrs.push(strPtr(`${key}=${this.env[key]}`));
+ });
+ argvPtrs.push(0);
+
+ const argv = offset;
+ argvPtrs.forEach((ptr) => {
+ this.mem.setUint32(offset, ptr, true);
+ this.mem.setUint32(offset + 4, 0, true);
+ offset += 8;
+ });
+
+ // The linker guarantees global data starts from at least wasmMinDataAddr.
+ // Keep in sync with cmd/link/internal/ld/data.go:wasmMinDataAddr.
+ const wasmMinDataAddr = 4096 + 8192;
+ if (offset >= wasmMinDataAddr) {
+ throw new Error("total length of command line and environment variables exceeds limit");
+ }
+
+ this._inst.exports.run(argc, argv);
+ if (this.exited) {
+ this._resolveExitPromise();
+ }
+ await this._exitPromise;
+ }
+
+ _resume() {
+ if (this.exited) {
+ throw new Error("Go program has already exited");
+ }
+ this._inst.exports.resume();
+ if (this.exited) {
+ this._resolveExitPromise();
+ }
+ }
+
+ _makeFuncWrapper(id) {
+ const go = this;
+ return function () {
+ const event = { id: id, this: this, args: arguments };
+ go._pendingEvent = event;
+ go._resume();
+ return event.result;
+ };
+ }
+ }
+
+ if (
+ typeof module !== "undefined" &&
+ global.require &&
+ global.require.main === module &&
+ global.process &&
+ global.process.versions &&
+ !global.process.versions.electron
+ ) {
+ if (process.argv.length < 3) {
+ console.error("usage: go_js_wasm_exec [wasm binary] [arguments]");
+ process.exit(1);
+ }
+
+ const go = new Go();
+ go.argv = process.argv.slice(2);
+ go.env = Object.assign({ TMPDIR: require("os").tmpdir() }, process.env);
+ go.exit = process.exit;
+ WebAssembly.instantiate(fs.readFileSync(process.argv[2]), go.importObject).then((result) => {
+ process.on("exit", (code) => { // Node.js exits if no event handler is pending
+ if (code === 0 && !go.exited) {
+ // deadlock, make Go print error and stack traces
+ go._pendingEvent = { id: 0 };
+ go._resume();
+ }
+ });
+ return go.run(result.instance);
+ }).catch((err) => {
+ console.error(err);
+ process.exit(1);
+ });
+ }
+})();
diff --git a/go.mod b/go.mod
new file mode 100644
index 0000000..4e27449
--- /dev/null
+++ b/go.mod
@@ -0,0 +1,5 @@
+module github.com/CrispyBaguette/wasm-palette-converter
+
+go 1.17
+
+require github.com/makeworld-the-better-one/dither/v2 v2.2.0 // indirect
diff --git a/go.sum b/go.sum
new file mode 100644
index 0000000..34f6d30
--- /dev/null
+++ b/go.sum
@@ -0,0 +1,8 @@
+github.com/davecgh/go-spew v1.1.0/go.mod h1:J7Y8YcW2NihsgmVo/mv3lAwl/skON4iLHjSsI+c5H38=
+github.com/makeworld-the-better-one/dither/v2 v2.2.0 h1:VTMAiyyO1YIO07fZwuLNZZasJgKUmvsIA48ze3ALHPQ=
+github.com/makeworld-the-better-one/dither/v2 v2.2.0/go.mod h1:VBtN8DXO7SNtyGmLiGA7IsFeKrBkQPze1/iAeM95arc=
+github.com/pmezard/go-difflib v1.0.0/go.mod h1:iKH77koFhYxTK1pcRnkKkqfTogsbg7gZNVY4sRDYZ/4=
+github.com/stretchr/objx v0.1.0/go.mod h1:HFkY916IF+rwdDfMAkV7OtwuqBVzrE8GR6GFx+wExME=
+github.com/stretchr/testify v1.6.1/go.mod h1:6Fq8oRcR53rry900zMqJjRRixrwX3KX962/h/Wwjteg=
+gopkg.in/check.v1 v0.0.0-20161208181325-20d25e280405/go.mod h1:Co6ibVJAznAaIkqp8huTwlJQCZ016jof/cbN4VW5Yz0=
+gopkg.in/yaml.v3 v3.0.0-20200313102051-9f266ea9e77c/go.mod h1:K4uyk7z7BCEPqu6E+C64Yfv1cQ7kz7rIZviUmN+EgEM=
diff --git a/main.go b/main.go
new file mode 100644
index 0000000..aecd575
--- /dev/null
+++ b/main.go
@@ -0,0 +1,10 @@
+package main
+
+import (
+ "syscall/js"
+)
+
+func main() {
+ js.Global().Set("DitherNord", DitherNord())
+ <-make(chan bool)
+}
diff --git a/wasm.go b/wasm.go
new file mode 100644
index 0000000..67524c8
--- /dev/null
+++ b/wasm.go
@@ -0,0 +1,113 @@
+package main
+
+import (
+ "bytes"
+ b64 "encoding/base64"
+ "encoding/hex"
+ "image"
+ "image/color"
+ _ "image/jpeg"
+ "image/png"
+ "log"
+ "syscall/js"
+ "time"
+
+ "github.com/makeworld-the-better-one/dither/v2"
+)
+
+var nordPalette, _ = buildPalette([]string{
+ "2e3440",
+ "3b4252",
+ "434c5e",
+ "4c566a",
+ "d8dee9",
+ "e5e9f0",
+ "eceff4",
+ "8fbcbb",
+ "88c0d0",
+ "81a1c1",
+ "5e81ac",
+ "bf616a",
+ "d08770",
+ "ebcb8b",
+ "a3be8c",
+ "b48ead",
+})
+
+func buildPalette(pal []string) (color.Palette, error) {
+ var palette = make(color.Palette, len(pal))
+
+ for i, s := range pal {
+ b, err := hex.DecodeString(s)
+ if err != nil {
+ return nil, err
+ }
+ palette[i] = color.RGBA{b[0], b[1], b[2], 0xff}
+ }
+
+ return palette, nil
+}
+
+func ditherImage(img image.Image) image.Image {
+ // Build ditherer
+ ditherer := dither.NewDitherer(nordPalette)
+ ditherer.Matrix = dither.FloydSteinberg
+
+ // Dither image in a copy
+ dst := ditherer.DitherCopy(img)
+
+ return dst
+}
+
+func decodeImage(imageData []byte) (image.Image, error) {
+ img, imageType, err := image.Decode(bytes.NewReader(imageData))
+ if err != nil {
+ return nil, err
+ }
+ log.Printf("Decoded image as %v\n", imageType)
+ return img, nil
+}
+
+// DittherNord returns a Promise that takes a UintArray containing a Jpeg or png image,
+// and resolves to a string containing a base64 encoded png image.
+func DitherNord() js.Func {
+ return js.FuncOf(func(this js.Value, args []js.Value) interface{} {
+ imageBytes := make([]byte, args[0].Length())
+ js.CopyBytesToGo(imageBytes, args[0])
+
+ handler := js.FuncOf(func(this js.Value, args []js.Value) interface{} {
+ resolve := args[0]
+ reject := args[1]
+
+ go func() {
+ // Decode image from raw bytes
+ img, err := decodeImage(imageBytes)
+ if err != nil {
+ errorConstructor := js.Global().Get("Error")
+ errorObject := errorConstructor.New(err.Error())
+ reject.Invoke(errorObject)
+ }
+
+ // Perform dithering
+ log.Println("Dithering image...")
+ t1 := time.Now()
+ ditheredImage := ditherImage(img)
+ t2 := time.Now()
+ log.Printf("Image dithered in %v\n", t2.Sub(t1))
+
+ // Encode as PNG
+ buf := new(bytes.Buffer)
+ png.Encode(buf, ditheredImage)
+
+ // Encode as img src b64 string and resolve
+ encodedImage := b64.StdEncoding.EncodeToString(buf.Bytes())
+ resolve.Invoke(js.ValueOf(encodedImage))
+ }()
+
+ return nil
+ })
+
+ promiseConstructor := js.Global().Get("Promise")
+ return promiseConstructor.New(handler)
+ })
+}