@saschazar/wasm-image-loader

📦 WebAssembly image loader/resizer

A dependency-free image loader/resizer written in WebAssembly

It works primarily as JPEG/PNG decoder, but might as well load 'raw' images from a Uint8Array to resize them to a desired width/height.

Installation

yarn add @saschazar/wasm-image-loader

or

npm install --save @saschazar/wasm-image-loader

Usage

It supports usage in the browser, in a Web Worker and of course Node.js.

// Node.js
import wasm_image_loader from '@saschazar/wasm-image-loader';

// Web Worker - see: https://developer.mozilla.org/en-US/docs/Web/API/WorkerGlobalScope/importScripts
importScripts('wasm_image_loader.js');

// -------- Browser/Web Worker/Node.js code below --------

// Load an image into a buffer using the Fetch API
const buffer = fetch('some JPEG or PNG').then((res) => res.buffer());

// Initialize the WebAssembly Module
const imageLoaderModule = new Promise((resolve) => {
  const wasm = wasm_image_loader({
    onRuntimeInitialized() {
      // remove the 'then' property from wasm_image_loader,
      // otherwise Promise runs into an endless loop.
      const { then, ...other } = wasm;
      // let Promise resolve with 'other' properties.
      resolve(other);
    },
  });
});

async function loadImage() {
  // store image buffer in Uint8Array
  const array = new Uint8Array(await buffer());
  const channels = 3; // 3 if RGB, 4 if Alpha channel is present (e.g. PNG)

  // let imageLoaderModule Promise resolve
  const { decode, dimensions, free, resize } = await imageLoaderModule;

  const decoded = decode(array, array.length, channels);
  const { channels, height, width } = dimensions();
  const resized = resize(decoded, width, height, channels, 800, 600);
  console.log(resized); // logs the uncompressed 800x600 RGB Uint8Array

  // clean up memory, when loader is not needed anymore
  free();
}

Example

A working example is available on RunKit.

Credits

This package uses nothings/stb's source code (stb_image.h and stb_image_resize.h in particular).

License

Licensed under the MIT license.

Copyright ©️ 2020—2021 Sascha Zarhuber