icodec

Image encoders & decoders built with WebAssembly, support high-depth.

Module	Encoder	Decoder	Bit Depth
jpeg	MozJPEG		8
png	OxiPNG + imagequant	image-png	8, 16
qoi	qoi		8
webp	libwebp		8
heic	libheif + x265	libheif + libde265	8, 10, 12
avif	libavif + aom		8, 10, 12, 16*
jxl	libjxl		from 8 to 16
wp2	libwebp2		8

Warning

Since libheif does not support specify thread count for x265 encoder, The encode of the heic module only work in webworker.

* 16-bit AVIF uses experimental simple transform that store image in 12-bit + extra 4-bit hidden image item.

icodec is aimed at the web platform and has some limitations:

• Decode output & Encode input only support RGBA format.
• No animated image support, you should use video instead.

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");
const data = new Uint8Array(await response.arrayBuffer());

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

// Decode AVIF to ImageData.
const image = avif.decode(data);

// This should be called once before you invoke `encode()`
await jxl.loadEncoder();

// Encode the image to JPEG XL.
const jxlData = jxl.encode(image/*, { options }*/);

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.

icodec is tree-shakable, with a bundler the unused code and wasm files can be eliminated.

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);

Type of each codec module:

/**
 * Provides a uniform type for codec modules that support encoding.
 *
 * @example
 * import { wp2, ICodecModule } from "icodec";
 *
 * const encoder: ICodecModule<wp2.Options> = wp2;
 */
interface ICodecModule<T = any> {
  /**
   * The default options of `encode` function.
   */
  defaultOptions: Required<T>;

  /**
   * The MIME type string of the format.
   */
  mimeType: string;

  /**
   * File extension (without the dot) of this format.
   */
  extension: string;

  /**
   * List of supported bit depth, from lower to higher.
   */
  bitDepth: number[];

  /**
   * Load the decoder WASM file, must be called once before decode.
   * Multiple calls are ignored, and return the first result.
   *
   * @param source If pass a string, it's the URL of WASM file to fetch,
   *               else it will be treated as the WASM bytes.
   * @return the underlying WASM module, which is not part of
   *               the public API and can be changed at any time.
   */
  loadDecoder(source?: WasmSource): Promise<any>;

  /**
   * Convert the image to raw RGBA data.
   */
  decode(input: Uint8Array): ImageData;

  /**
   * Load the encoder WASM file, must be called once before encode.
   * Multiple calls are ignored, and return the first result.
   *
   * @param source If pass a string, it's the URL of WASM file to fetch,
   *               else it will be treated as the WASM bytes.
   * @return the underlying WASM module, which is not part of
   *               the public API and can be changed at any time.
   */
  loadEncoder(source?: WasmSource): Promise<any>;

  /**
   * Encode an image with RGBA pixels data.
   */
  encode(image: ImageDataLike, options?: T): Uint8Array;
}

The png module exports extra members:

/**
 * Reduces the colors used in the image at a slight loss, using a combination
 * of vector quantization algorithms.
 *
 * Can be used before other compression algorithm to boost compression ratio.
 */
declare function reduceColors(image: ImageDataLike, options?: QuantizeOptions): Uint8Array;

High Bit-Depth

icodec supports high bit-depth images, for image with bit-depth > 8, the data should be 2-bytes per channel in Little-Endian (both encode input and decode result).

If you want to encode an image with bit-depth does not supported by the codec, you must scale it before.

In browser, decode result of the 8-bit image is an instance of ImageData, otherwise is not.

Performance

Decode & Encode test/snapshot/image.* files, 417px x 114px, 8-bit, time.SD is Standard Deviation of the time.

This benchmark ignores extra code size introduced by icodec, which in practice needs to be taken into account.

Decode on Edge browser.

No.	Name	codec	time	time.SD
0	icodec	avif	2.30 ms	19.02 us
1	2d	avif	1.46 ms	6.34 us
2	WebGL	avif	2.78 ms	12.80 us
3	icodec	heic	2.55 ms	9.82 us
4	icodec	jpeg	719.84 us	3.00 us
5	2d	jpeg	584.23 us	2.52 us
6	WebGL	jpeg	1,674.88 us	5.84 us
7	icodec	jxl	3.51 ms	30.08 us
8	icodec	png	336.74 us	1.21 us
9	2d	png	561.65 us	2.14 us
10	WebGL	png	1,654.59 us	18.81 us
11	icodec	qoi	432.43 us	1.44 us
12	icodec	webp	779.77 us	2.38 us
13	2d	webp	799.01 us	1.48 us
14	WebGL	webp	1,952.10 us	2.55 us
15	icodec	wp2	2.55 ms	12.66 us

Decode on Node, vs Sharp.

No.	Name	codec	time	time.SD
0	icodec	avif	2.01 ms	3.24 us
1	Sharp	avif	2.54 ms	10.39 us
2	icodec	heic	2.28 ms	4.41 us
3	icodec	jpeg	470.25 us	2.96 us
4	Sharp	jpeg	836.00 us	1.24 us
5	icodec	jxl	3.22 ms	290.77 us
6	icodec	png	109.22 us	883.82 ns
7	Sharp	png	637.05 us	1,947.88 ns
8	icodec	qoi	191.46 us	1.18 us
9	icodec	webp	548.78 us	600.09 ns
10	Sharp	webp	1,700.14 us	7,637.86 ns
11	icodec	wp2	2.28 ms	2.86 us

Encode on Node, vs Sharp. Note that icodec and Sharp do not use the same code, so the output images are not exactly equal.

No.	Name	codec	time	time.SD
0	icodec	avif	47.47 ms	78.77 us
1	Sharp	avif	52.77 ms	78.89 us
2	icodec	jpeg	7,664.33 us	3.62 us
3	Sharp	jpeg	802.02 us	2.95 us
4	icodec	jxl	32.05 ms	37.34 us
5	icodec	png	70.11 ms	132.71 us
6	Sharp	png	10.88 ms	69.48 us
7	icodec	qoi	371.47 us	666.00 ns
8	icodec	webp	4.42 ms	3.17 us
9	Sharp	webp	4.04 ms	13.09 us
10	icodec	wp2	90.14 ms	295.49 us

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

build the project:

pnpm exec tsc
node scripts/build.js

Run tests:

node --test test/test-*.js

Start web demo:

node scripts/start-demo.js

TODOs:

• Could it be possible to remove HEIC & VVIC encoder dependency on pthread, or limit the number of threads?
• Cannot specify vvenc & vvdec paths for libheif build.