Generate responsive HTML picture elements powered by on-the-fly Filestack image conversions.

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Table of Contents

• What is Adaptive
  • Features
• Usage
  • Browser
    • SRI
  • Node (react example)
    • Use with JSX
  • Storage aliases and external urls
  • Image width and pixel density
  • Webcomponent
  • Using width descriptors
  • WebP support
  • Custom CNAME
  • Transformations support
    • Disable validator
• Development
• Documentation
• Contributing
• Future

What is Adaptive

Adaptive is a tool which allow Filestack users to combine the power of on-the-fly image processing with the latest standard for responsive web images.

This library ships with a built-in virtual DOM adapter powered by hyperx, which allows you to simply call picture(source, options, renderer), where renderer can be any DOM builder supported by hyperx (e.g React.createElement). If renderer is not provided then picture will default to returning plain DOM.

Features

• Focus on usability and performance
• Works with Filestack handles, storage aliases and external urls
• Support for different sizes and formats in srcSet
• Allows you to add some image transformations
• Easily integrable with external virtual DOM renderers

Usage

Browser

You can find the newest version at https://static.filestackapi.com/adaptive/1.3.0/adaptive.min.js

    <script src="https://static.filestackapi.com/adaptive/1.3.0/adaptive.min.js" crossorigin="anonymous"></script>
    <script>
        const options = {
            alt: 'windsurfer',
            sizes: {
                fallback: '60vw',
            }
        };
        const el = fsAdaptive.picture(FILESTACK_HANDLE, options);
        document.body.appendChild(el);
    </script>

Output:

<picture>
    <img src="https://cdn.filestackcontent.com/5aYkEQJSQCmYShsoCnZN"
         srcset="
            https://cdn.filestackcontent.com/resize=width:180/5aYkEQJSQCmYShsoCnZN 180w, 
            https://cdn.filestackcontent.com/resize=width:360/5aYkEQJSQCmYShsoCnZN 360w, 
            https://cdn.filestackcontent.com/resize=width:540/5aYkEQJSQCmYShsoCnZN 540w, 
            https://cdn.filestackcontent.com/resize=width:720/5aYkEQJSQCmYShsoCnZN 720w, 
            https://cdn.filestackcontent.com/resize=width:900/5aYkEQJSQCmYShsoCnZN 900w, 
            https://cdn.filestackcontent.com/resize=width:1080/5aYkEQJSQCmYShsoCnZN 1080w, 
            https://cdn.filestackcontent.com/resize=width:1296/5aYkEQJSQCmYShsoCnZN 1296w, 
            https://cdn.filestackcontent.com/resize=width:1512/5aYkEQJSQCmYShsoCnZN 1512w, 
            https://cdn.filestackcontent.com/resize=width:1728/5aYkEQJSQCmYShsoCnZN 1728w, 
            https://cdn.filestackcontent.com/resize=width:1944/5aYkEQJSQCmYShsoCnZN 1944w, 
            https://cdn.filestackcontent.com/resize=width:2160/5aYkEQJSQCmYShsoCnZN 2160w, 
            https://cdn.filestackcontent.com/resize=width:2376/5aYkEQJSQCmYShsoCnZN 2376w, 
            https://cdn.filestackcontent.com/resize=width:2592/5aYkEQJSQCmYShsoCnZN 2592w,
            https://cdn.filestackcontent.com/resize=width:2808/5aYkEQJSQCmYShsoCnZN 2808w, 
            https://cdn.filestackcontent.com/resize=width:3024/5aYkEQJSQCmYShsoCnZN 3024w"
         alt="photo_01" 
         sizes="60vw">
</picture>

SRI

Subresource Integrity (SRI) is a security feature that enables browsers to verify that files they fetch (for example, from a CDN) are delivered without unexpected manipulation. It works by allowing you to provide a cryptographic hash that a fetched file must match

To obtain sri hashes for adaptive library check manifest.json file on CDN:

https://static.filestackapi.com/adaptive/{LIBRARY_VERSION}/manifest.json

<script src="//static.filestackapi.com/adaptive/{LIBRARY_VERSION}/adaptive.min.js" integrity="{FILE_HASH}" crossorigin="anonymous"></script>

Where {LIBRARY_VERSION} is currently used library version and {FILE_HASH} is one of the hashes from integrity field in manifest.json file

Node (react example)

npm install filestack-adaptive

import react from 'react';
import reactDOM from 'react-dom';
import { picture } from 'filestack-adaptive';

// Need to spread children parameter to prevent React key warnings
const createElement = (Component, props, children) => {
  return React.createElement(Component, props, ...children);
};

const options = { alt: 'windsurfer', sizes: { fallback: '100vw' } };
const tree = picture(FILESTACK_HANDLE, options, createElement);
ReactDOM.render(tree, document.body);

Use with JSX

In a case of need to create your own <picture/> element you can call makePictureTree directly in your JSX

import React, { Component } from 'react';
import { makePictureTree } from 'filestack-adaptive';

class Picture extends Component {
  renderSources(sources) {
    return sources.map((sourceObj) => {
      return <source {...sourceObj} />;
    });
  }
  renderImage(imageObj) {
    return <img {...imageObj} />;
  }
  render() {
    const tree = makePictureTree(this.props.handle, this.props);
    return (
      <picture>
        {tree.sources && this.renderSources(tree.sources)}
        {this.renderImage(tree.img)}
      </picture>
    );
  }
}

export default Picture;

Storage aliases and external urls

You can also use Filestack storage alias or external urls as an image source:

  <script src="https://static.filestackapi.com/adaptive/1.3.0/adaptive.min.js"></script>
  <script>
      const options = {
          alt: 'windsurfer',
          sizes: {
              fallback: '60vw',
          }
      };
      const srcHandle1 = {
        srcHandle: 'src://your_storage_alias_name/example.jpg',
        apiKey: 'YOUR_FILESTACK_API_KEY'
      };
      const el1 = fsAdaptive.picture(srcHandle1, options);
      document.body.appendChild(el1);


      const srcHandle2 = {
        srcHandle: 'https://yourdomain.com/photo1.jpg,
        apiKey: 'YOUR_FILESTACK_API_KEY'
      };
      const el2 = fsAdaptive.picture(srcHandle2, options);
      document.body.appendChild(el2);
  </script>

Image width and pixel density

When the image width is known it will generate a srcset for HiDPI screens at 2x. More densities can be specified by passing an array to the resolutions option, e.g. resolutions: ['1x', '2x', '3x'].

const options = {
  alt: 'windsurfer', 
  width: '768px',
};
picture(FILESTACK_HANDLE, options);

Output:

<picture>
  <img src="https://cdn.filestackcontent.com/resize=width:768/5aYkEQJSQCmYShsoCnZN" 
       srcset="https://cdn.filestackcontent.com/resize=width:768/5aYkEQJSQCmYShsoCnZN 1x, 
               https://cdn.filestackcontent.com/resize=width:1536/5aYkEQJSQCmYShsoCnZN 2x" 
       alt="windsurfer" 
       width="768">
</picture>

Webcomponent

Adaptive now supports webcomponent. Supported options: src, width, alt, cname, policy, signature, keys, resolutions

<fs-adaptive src="NxW2v528S9W6K1l5LnFS" width="769px" alt="windsurfer" ></fs-adaptive>

Output:

<picture>
  <img src="https://cdn.filestackcontent.com/resize=width:768/NxW2v528S9W6K1l5LnFS" 
       srcset="https://cdn.filestackcontent.com/resize=width:768/NxW2v528S9W6K1l5LnFS 1x, 
               https://cdn.filestackcontent.com/resize=width:1536/NxW2v528S9W6K1l5LnFS 2x" 
       alt="windsurfer" 
       width="768">
</picture>

Using width descriptors

You can specify generated widths by using resolutions, which takes an array of numbers or strings (e.g. 540 or '540w').

const options = {
  alt: 'windsurfer', 
  sizes: {
    '(min-width: 1080px)': '100vw',
    fallback: '90vw',
  },
  resolutions: [540, 1080],
};
picture(FILESTACK_HANDLE, options);

Output:

<picture>
  <source media="(min-width: 1080px)" 
          sizes="100vw" 
          srcset="https://cdn.filestackcontent.com/resize=width:540/5aYkEQJSQCmYShsoCnZN 540w, 
          https://cdn.filestackcontent.com/resize=width:1080/5aYkEQJSQCmYShsoCnZN 1080w"> 
  <img src="https://cdn.filestackcontent.com/5aYkEQJSQCmYShsoCnZN" 
       srcset="https://cdn.filestackcontent.com/resize=width:540/5aYkEQJSQCmYShsoCnZN 540w, 
               https://cdn.filestackcontent.com/resize=width:1080/5aYkEQJSQCmYShsoCnZN 1080w" 
       alt="windsurfer" 
       sizes="90vw">
</picture>

WebP support

WebP can be used when it's supported by the browser. Filestack will take care of the image conversion and cache it on the delivery network for future requests.

const options = {
  alt: 'windsurfer', 
  formats: ['webp', 'jpg'], // order matters!
};
picture(FILESTACK_HANDLE, options);

Output:

<picture>
  <source srcset="https://cdn.filestackcontent.com/output=format:webp/5aYkEQJSQCmYShsoCnZN" 
          type="image/webp">
  <source srcset="https://cdn.filestackcontent.com/output=format:jpg/5aYkEQJSQCmYShsoCnZN" 
          type="image/jpg"> 
  <img src="https://cdn.filestackcontent.com/5aYkEQJSQCmYShsoCnZN" alt="windsurfer">
</picture>

Custom CNAME

In order to use custom cname for generated file links just use cname option:

const options = {
  cname: 'fs.test123.com'
};
picture(FILESTACK_HANDLE, options);

Output:

<picture>
  <img src="https://cdn.fs.test123.com/5aYkEQJSQCmYShsoCnZN">
</picture>

Transformations support

Adaptive also supports Filestack transformations. Available options are listed in doc:

https://www.filestack.com/docs/image-transformations

const options = {
  alt: 'windsurfer', 
  width: 400,
  transforms: {
    blur: {
      amount: 5
    },
    border: true, // use default options of border transformation
  }
};
picture(FILESTACK_HANDLE, options);

Output:

<picture>
  <img src="https://cdn.filestackcontent.com/blur=amount:5/border/resize=width:400/5aYkEQJSQCmYShsoCnZN" srcset="https://cdn.filestackcontent.com/blur=amount:5/border/resize=width:400/5aYkEQJSQCmYShsoCnZN 1x, https://cdn.filestackcontent.com/blur=amount:5/border/resize=width:800/5aYkEQJSQCmYShsoCnZN 2x" alt="windsurfer" width="400">
</picture>

Disable validator

To speed up generating of final output (useful when you have a bunch of images on your site) you can optionally disable validation of transformation params by passing additional prop in options:

const options = {
  ...
  useValidator: false,
  ...
}

Development

To install and work on Adaptiv locally:

git clone git@github.com:filestack/adaptive.git
cd adaptive
npm install

To create build directory:

npm run build

This newly created directory contains

build/
├── browser/                # for the UMD module (usable in HTML script tags)
   └── index.umd.js         #
├── main/                   # for the CommonJS module
   ├── ...                  #
   └── index.js             # 
└── module/                 # for the ES Module (suitable for bundlers like Webpack and Rollup)
   ├── ...                  #
   └── index.js             #

Documentation

For more info about available methods and options check browser documentation:
https://filestack.github.io/adaptive/

Contributing

We follow the conventional commits specification to ensure consistent commit messages and changelog formatting.

Future

Adaptive is joining an ecosystem already populated with many utilities for responsive images. We want to remain flexible while still having some opinions on how to implement picture elements using Filestack conversions, and we know it is hard to cover every use case. Contributions and ideas are welcome that would help improve the usefulness of this library.

Current ideas:

• LQIP using the Filestack blur transformation
• Compress HiDPI images using Filestack compress task
• Implement art direction with Filestack crop
• Develop a PostHTML transform for post-processing HTML using makePictureTree