png

@jsquash/png

An easy experience for encoding and decoding PNG images in the browser. Powered by WebAssembly ⚡️.

Uses the rust PNG crate.

A jSquash package. Codecs and supporting code derived from the Squoosh app.

Installation

npm install --save @jsquash/png
# Or your favourite package manager alternative

Usage

Note: You will need to either manually include the wasm files from the codec directory or use a bundler like WebPack or Rollup to include them in your app/server.

decode(data: ArrayBuffer): Promise

Decodes PNG binary ArrayBuffer to raw RGB image data.

data

Type: ArrayBuffer

Example

import { decode } from '@jsquash/png';

const formEl = document.querySelector('form');
const formData = new FormData(formEl);
const imageData = await decode(await formData.get('image').arrayBuffer());

encode(data: ImageData): Promise

ℹ️ You may want to use the @jsquash/oxipng package instead. It can both optimise and encode to PNG directly from raw image data.

Encodes raw RGB image data to PNG format and resolves to an ArrayBuffer of binary data.

data

Type: ImageData

Example

import { encode } from '@jsquash/png';

async function loadImage(src) {
  const img = document.createElement('img');
  img.src = src;
  await new Promise(resolve => img.onload = resolve);
  const canvas = document.createElement('canvas');
  [canvas.width, canvas.height] = [img.width, img.height];
  const ctx = canvas.getContext('2d');
  ctx.drawImage(img, 0, 0);
  return ctx.getImageData(0, 0, img.width, img.height);
}

const rawImageData = await loadImage('/example.jpg');
const pngBuffer = await encode(rawImageData);

Manual WASM initialisation (not recommended)

In most situations there is no need to manually initialise the provided WebAssembly modules. The generated glue code takes care of this and supports most web bundlers.

One situation where this arises is when using the modules in Cloudflare Workers (See the README for more info).

The encode and decode modules both export an init function that can be used to manually load the wasm module.

import decode, { init as initPngDecode } from '@jsquash/png/decode';

initPngDecode(WASM_MODULE); // The `WASM_MODULE` variable will need to be sourced by yourself and passed as an ArrayBuffer.
const image = await fetch('./image.png').then(res => res.arrayBuffer()).then(decode);