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browser-image-resizer

A tiny (~7kb uncompressed, ~1kb compressed) browser-based library to downscale and/or resize images using <canvas>.

Introduction

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

Installation

NPM/Yarn

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

Browser

<script src="https://cdn.jsdelivr.net/gh/ericnograles/[email protected]/dist/index.js"></script>

Usage

NPM/Yarn

Promises

import { readAndCompressImage } from 'browser-image-resizer';

const config = {
  quality: 0.5,
  maxWidth: 800,
  maxHeight: 600,
  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);
  });

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);
  }
}

Browser

Promises

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

// Note: A single file comes from event.target.files on <input>
BrowserImageResizer.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);
  });

Async/Await

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 BrowserImageResizer.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 image 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 an Image Blob

Contributing

The fastest way to contribute back is to fork the repl.it of this repo (https://replit.com/@grales/browser-image-resizer). Please open any Issues if you have trouble spinning it up.

repl.it First-time Setup

Upon forking of the repl.it, open a new Shell and follow these instructions:

  1. Execute npm link at the top ~/browser-image-resizer folder
  2. Execute cd tests/bir-vue
  3. Execute npm i && npm link browser-image-resizer && npm run serve
  4. Your repl.it should automatically boot to a webview of a Vue 3 CLI SPA
  • This SPA will point to your built copy of browser-image-resizer that runs automatically when the repl.it boots
  1. Modify any code at the top level src/ and it will reflect on your Vue 3 CLI SPA test app

repl.it Specifics

  • The repl.it above is configured to run the dev script of the library, which is a webpack-dev-server that auto-generates the dist/ library which is the entry point of this library
  • The subsequent commands gives you an actual web application on which to verify your changes
  • If you prefer, you can do this locally as well, but the repl.it ensures a faster and more consistent onboarding