danleininger / browser-image-resizer

A browser-based utility to downscale and resize images using canvas

browser-image-resizer

Introduction

This library allows for cross-browser image downscaling and resizing utilizing <canvas>. The code was part of Ross Turner's HTML5-ImageUploader. Note that this is meant to be a browser-only utility and will not work in Node.js.

Demo

https://browser-image-resizer-test.firebaseapp.com/

Installation

• npm install browser-image-resizer
• yarn add browser-image-resizer

Sample - Promises

import readAndCompressImage from 'browser-image-resizer';

const config = {
  quality: 0.5,
  maxWidth: 800,
  maxHeight: 600,
  autoRotate: true,
  debug: true
};

// Note: A single file comes from event.target.files on <input>
readAndCompressImage(file, config)
  .then(resizedImage => {
    // Upload file to some Web API
    const url = `http://localhost:3001/upload`;
    const formData = new FormData();
    formData.append('images', resizedImage);
    const options = {
      method: 'POST',
      body: formData
    };

    return fetch(url, options);
  })
  .then(result => {
    // TODO: Handle the result
    console.log(result);
  });

Sample - Async/Await

import readAndCompressImage from 'browser-image-resizer';

const config = {
  quality: 0.7,
  width: 800,
  height: 600
};

// Note: A single file comes from event.target.files on <input>
async function uploadImage(file) {
  try {
    let resizedImage = await readAndCompressImage(file, config);

    const url = `http://localhost:3001/upload`;
    const formData = new FormData();
    formData.append('images', resizedImage);
    const options = {
      method: 'POST',
      body: formData
    };

    let result = await fetch(url, options);

    // TODO: Handle the result
    console.log(result);
    return result;
  } catch (error) {
    console.error(error);
    throw(error);
  }
}

readAndCompressImage(file, config) => Promise

Inputs

• file: A File object, usually from an <input>
• config: See below

Property Name	Purpose	Default Value
quality	The quality of the JPEG	0.5
maxWidth	The maximum width for the downscaled image	800
maxHeight	The maximum height for the downscaled image	600
autoRotate	Reads EXIF data on the image to determine orientation	true
debug	console.log image update operations	false
mimeType	specify image output type other than jpeg	'image/jpeg'

Outputs

A Promise that yields a JPEG Blob