Basic functionality sort of works

This commit is contained in:
CrispyBaguette 2021-12-11 16:19:48 +01:00
parent aef91275c9
commit c8adda79db
8 changed files with 996 additions and 86 deletions

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@ -3,3 +3,5 @@ build-wasm:
build-react: build-react:
cd client && npm run build cd client && npm run build
all: build-wasm build-react

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@ -15,6 +15,38 @@
</head> </head>
<body> <body>
<noscript>You need to enable JavaScript to run this app.</noscript> <noscript>You need to enable JavaScript to run this app.</noscript>
<article>
<h1>Go+Wasm image dithering tool</h1>
<aside>Featuring the Nord Color Palette</aside>
<p>
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.
</p>
<p>
Running in the browser with Wasm causes a bit of a performance penalty.
Multithreading is not available (not that it matters much since
Floyd-Steinberg is single-threaded), and sending data back and forth
between JS and Wasm can take a little while.
</p>
<p>
I've re-used code from
<a
href="https://www.sitepen.com/blog/using-webassembly-with-web-workers"
>
this article
</a>
to make the Wasm code run in a web worker, with some adaptations for Go
oddities.
</p>
<p>
If you're into that sort of thing, source code is available on
<a href="https://github.com/CrispyBaguette/wasm-palette-converter">
GitHub
</a>
.
</p>
</article>
<div id="root"></div> <div id="root"></div>
</body> </body>
</html> </html>

744
client/public/wasm_exec.js Normal file
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@ -0,0 +1,744 @@
/* eslint-disable no-undef */
/* eslint-disable no-restricted-globals */
// 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);
});
}
})();

61
client/public/worker.js Normal file
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@ -0,0 +1,61 @@
importScripts("./wasm_exec.js");
if (!WebAssembly.instantiateStreaming) {
WebAssembly.instantiateStreaming = async (resp, importObject) => {
const source = await (await resp).arrayBuffer();
return await WebAssembly.instantiate(source, importObject);
};
}
// Create promise to handle Worker calls whilst
// module is still initialising
let wasmResolve;
const wasmReady = new Promise((resolve) => {
wasmResolve = resolve;
});
const go = new self.Go();
addEventListener(
"message",
async (e) => {
const { eventType, eventData, eventId } = e.data;
if (eventType === "INITIALISE") {
const instantiatedSource = await WebAssembly.instantiateStreaming(
fetch(eventData),
go.importObject
);
go.run(instantiatedSource.instance);
// Go does nor exposes the exports in the instantiated module :(((
const methods = ["DitherNord"];
wasmResolve(methods);
postMessage({
eventType: "INITIALISED",
eventData: methods,
});
} else if (eventType === "CALL") {
await wasmReady;
try {
const method = self[eventData.method];
const result = await method.apply(null, eventData.arguments);
self.postMessage({
eventType: "RESULT",
eventData: result,
eventId: eventId,
});
} catch (e) {
console.error(e);
self.postMessage({
eventType: "ERROR",
eventData:
"An error occured executing WASM instance function: " +
error.toString(),
eventId: eventId,
});
}
}
},
false
);

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@ -1,41 +1,10 @@
@media (prefers-color-scheme: dark) {
body {
color: #fff;
background: #000;
}
a:link {
color: #9cf;
}
a:hover,
a:visited:hover {
color: #cef;
}
a:visited {
color: #c9f;
}
}
body {
margin: 1em auto;
max-width: 40em;
padding: 0 0.62em;
font: 1.2em/1.62 sans-serif;
}
h1,
h2,
h3 {
line-height: 1.2;
}
.container {
display: flex;
flex-direction: column;
justify-content: center;
}
#output { #output {
max-width: 100%; image-rendering: optimizeSpeed; /* Legal fallback */
align-self: center; image-rendering: -moz-crisp-edges; /* Firefox */
} image-rendering: -o-crisp-edges; /* Opera */
@media print { image-rendering: -webkit-optimize-contrast; /* Safari */
body { image-rendering: optimize-contrast; /* CSS3 Proposed */
max-width: none; image-rendering: crisp-edges; /* CSS4 Proposed */
} image-rendering: pixelated; /* CSS4 Proposed */
-ms-interpolation-mode: nearest-neighbor; /* IE8+ */
} }

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@ -1,43 +1,117 @@
import React from 'react'; import React, { useEffect } from "react";
import './App.css'; import "./App.css";
function App() { function App() {
const [imageSrc, setImageSrc] = React.useState("");
const [displayOutput, setDisplayOutput] = React.useState(false);
const fileInput = React.useRef<HTMLInputElement>(null);
const handleClick = async () => {
if (!fileInput.current) {
return;
}
const workerProxy: any = await wasmWorker("main.wasm");
setDisplayOutput(false);
setImageSrc("");
// Check if a file was selected
if (fileInput.current.files!.length === 0) {
alert("No file selected");
return;
}
const reader = new FileReader();
reader.readAsArrayBuffer(fileInput.current.files![0]);
reader.onloadend = async (evt) => {
if (evt.target!.readyState === FileReader.DONE) {
const imageData = new Uint8Array(evt.target!.result as ArrayBuffer);
const ditheredImage = await workerProxy.DitherNord(imageData);
const outputValue = `data:image/png;base64,${ditheredImage}`;
setImageSrc(outputValue);
setDisplayOutput(true);
}
};
};
return ( return (
<article> <div className="App">
<h1>Go+Wasm image dithering tool</h1> <input
<aside>Featuring the Nord Color Palette</aside> type="file"
<p> id="source-image"
Load an image, click Go and wait (potentially for a while) for the image ref={fileInput}
to be dithered using the Nord color palette and the Floyd-Steinberg accept="image/png, image/jpeg"
algorithm. />
</p> <button id="go-btn" type="button" onClick={handleClick}>
<p> Go
Running in the browser with Wasm causes a bit of a performance penalty. </button>
Multithreading is not available (not that it matters much since <a id="output-wrapper" download="output.png" href={imageSrc}>
Floyd-Steinberg is single-threaded), and sending data back and forth <div className="container">
between JS and Wasm can take a little while. <img
</p> id="output"
<p> alt="dithering output"
I've re-used code from src={imageSrc}
<a style={{ display: displayOutput ? "block" : "none" }}
href="https://www.sitepen.com/blog/using-webassembly-with-web-workers" />
>this article</a </div>
> </a>
to make the Wasm code run in a web worker, with some adaptations for Go </div>
oddities.
</p>
<p>
If you're into that sort of thing, source code is available on
<a href="https://github.com/CrispyBaguette/wasm-palette-converter"
>GitHub</a
>.
</p>
<form>
<input type="file" id="source-image" accept="image/png, image/jpeg" />
<button id="go-btn" type="button" disabled>Go</button>
</form>
</article>
); );
} }
function wasmWorker(modulePath: string) {
// Create an object to later interact with
const proxy: any = {};
// Keep track of the messages being sent
// so we can resolve them correctly
let id = 0;
let idPromises: any = {};
return new Promise((resolve, reject) => {
const worker = new Worker("./worker.js");
worker.postMessage({ eventType: "INITIALISE", eventData: modulePath });
worker.addEventListener("message", function (event: any) {
const { eventType, eventData, eventId } = event.data;
if (eventType === "INITIALISED") {
const methods = event.data.eventData;
methods.forEach((method: any) => {
proxy[method] = (...args: any[]) => {
return new Promise((resolve, reject) => {
worker.postMessage({
eventType: "CALL",
eventData: {
method: method,
arguments: Array.from(args),
},
eventId: id,
});
idPromises[id] = { resolve, reject };
id++;
});
};
});
resolve(proxy);
return;
} else if (eventType === "RESULT") {
if (eventId !== undefined && idPromises[eventId]) {
idPromises[eventId].resolve(eventData);
delete idPromises[eventId];
}
} else if (eventType === "ERROR") {
if (eventId !== undefined && idPromises[eventId]) {
idPromises[eventId].reject(event.data.eventData);
delete idPromises[eventId];
}
}
});
worker.addEventListener("error", function (error: any) {
reject(error);
});
});
}
export default App; export default App;

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@ -1,13 +1,41 @@
@media (prefers-color-scheme: dark) {
body { body {
margin: 0; color: #fff;
font-family: -apple-system, BlinkMacSystemFont, 'Segoe UI', 'Roboto', 'Oxygen', background: #000;
'Ubuntu', 'Cantarell', 'Fira Sans', 'Droid Sans', 'Helvetica Neue', }
sans-serif; a:link {
-webkit-font-smoothing: antialiased; color: #9cf;
-moz-osx-font-smoothing: grayscale; }
a:hover,
a:visited:hover {
color: #cef;
}
a:visited {
color: #c9f;
}
}
body {
margin: 1em auto;
max-width: 40em;
padding: 0 0.62em;
font: 1.2em/1.62 sans-serif;
}
h1,
h2,
h3 {
line-height: 1.2;
}
.container {
display: flex;
flex-direction: column;
justify-content: center;
}
#output {
max-width: 100%;
align-self: center;
}
@media print {
body {
max-width: none;
} }
code {
font-family: source-code-pro, Menlo, Monaco, Consolas, 'Courier New',
monospace;
} }

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dist/main.wasm vendored

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