icodec

icodec

Image encoders & decoders built with WebAssembly.

Module	Encoder	Decoder
jpeg	MozJPEG
png	OxiPNG + imagequant	image-png
qoi	qoi
webp	libwebp
heic	libheif + x265	libheif + libde265
avif	libavif + aom
jxl	libjxl
wp2	libwebp2

[!WARNING] Since libheif does not support specify thread count for x265 encoder, call encode of the heic module must in webworker, and it does not support Node.

Usage

Requirement: The target environment must support WebAssembly SIMD.

pnpm add icodec

Use in browser:

// All codec modules (see the table above) are named export.
import { avif, jxl } from "icodec";

const response = await fetch("https://raw.githubusercontent.com/Kaciras/icodec/master/test/snapshot/image.avif")

// This should be called once before you invoke `decode()`
await avif.loadDecoder();

// Decode AVIF to ImageData.
const image = avif.decode(await response.arrayBuffer());

// Encode the image to JPEG XL, also need to load the encoder WASM first.
await jxl.loadEncoder();

/*
 * The image parameter must have properties:
 * {
 *     width: number;
 *     height: number;
 *     data: Uint8Array | Uint8ClampedArray;
 * }
 */
const encoded = jxl.encode(image, /*{ options }*/);

Each codec module exports:

• loadEncoder(input?): Load the encoder WASM file, must be called once before encode, it accepts an optional argument:

  • If pass a string, it's the URL of WASM file to fetch.
  • If pass a ArrayBuffer or ArrayBufferView, it will be treated as the WASM bytes.

  This function returns the underlying WASM module, which is not part of the public API and can be changed at any time.

• encode(imageData, options?): Encode an image with RGBA pixels data.

• loadDecoder(input?): Like loadEncoder, but for decode.

• decode(uint8Array): Convert the image to RGBA data, the return value is an ImageData type.

• mimeType: The MIME type string of the codec.

• extension: File extension of the format.

• defaultOptions: The default options for encode function.

• type Options: Type definition of the encode options.

The png module export extra members:

• reduceColors(imageData, options?): Reduces the colors used in the image at a slight loss, returns Uint8Array.
• type QuantizeOptions: Type definition of the options in reduceColors.

To use icodec in Node, just change the import specifier to icodec/node, and loadEncoder/loadDecoder will use readFileSync instead of fetch.

import { avif, jxl } from "icodec/node";

If your bundler requires special handing of WebAssembly, you can pass the URL of WASM files to load* function. WASM files are exported in the format icodec/<codec>-<enc|dec>.wasm.

import { avif, jxl } from "icodec";

// Example for Vite
import AVIFEncWASM from "icodec/avif-enc.wasm?url";
import JxlDecWASM from "icodec/jxl-dec.wasm?url";

await avif.loadDecoder(AVIFEncWASM);
await jxl.loadEncoder(JxlDecWASM);

Contribute

To build WASM modules, you will need to install:

• Cmake >= 3.24
• Rust & wasm-pack
• Emscripten
• Perl
• Git
• A proper C/C++ compiler toolchain, depending on your operating system

Run the build script:

node build.js

TODOs:

• Could it be possible to remove HEIC encoder dependency on pthread, or limit the number of threads?
• vvenc cannot be compiled with Emscripten.

Rnn tests:

pnpm exec tsc
node --test test/test-*.js

Start web demo:

node start-demo.js