progressive-image.js implements a progressively-loaded image effect similar to those seen on Facebook and Medium. A very small blurred image is replaced with the full-resolution equivalent when the element is scrolled into view.

Please use the code as you wish. Tweet me @craigbuckler if you find it useful and consider donating toward development.

Benefits:

saves unnecessary bandwidth
fast loading, high performance, images loaded on view
supports any image type (JPEG photographs are most appropriate)
supports responsive images (srcset and sizes attributes)
supports CSS background images
supports native lazy loading and aspect ratios
lightweight: 1,358 bytes of JavaScript, 407 bytes of CSS (minified)
any CSS reveal effect can be applied
no external dependencies - works with any framework
makes up to three attempts if images fail to download
works in all modern browsers (IE10+)
progressively-enhanced to work in older browsers
easy to use

View demonstration and full documentation...

Basic usage

Include the minified CSS and JavaScript anywhere in your page:

<link rel="stylesheet" href="https://cdn.jsdelivr.net/npm/progressive-image.js/dist/progressive-image.css">
<script src="https://cdn.jsdelivr.net/npm/progressive-image.js/dist/progressive-image.js"></script>

or use npm and a bundler:

npm i progressive-image.js

Then add progressively-loaded images:

<a href="full.jpg" class="progressive replace">
  <img src="tiny.jpg" class="preview" alt="image" />
</a>

where:

full.jpg is the large image.
tiny.jpg is a small preview image - typically 20px width.

Both images must have the same aspect ratio.

Refer to demo.html for full documentation, examples, options, and usage notes. It is also available as a CodePen demonstration page.

Version history

v1.6.0, 3 July 2020

improved browser support verification
more resilient to framework issues
minor refactoring
updated help and images
bugfix: script now works in HTML <head>

v1.5.0, 6 June 2020

pageshow event for Single Page Apps
more reliable MutationObserver
class names applied to the preview are applied to the full image (except preview)
smaller, better performance
no errors in older browsers
updated usage notes, including native lazy loading

v1.4.1, 9 July 2019

strict mode
srcset and sizes attributes only set when available
README and demo.html update

v1.4.0, 24 June 2019

retries download after 3s and 6s (suggestion from cheuksing)
continues to show preview if full image download fails
autoprefixer update

v1.3.0, 30 May 2019

Gulp.js minification
published on npm, CDN information

v1.2.0, 13 April 2018

added CSS background image support information

v1.2.0, 9 April 2018

full image replaces preview in-place (PR from ftaiolivista)
minor refactoring and simplification

v1.1.0, 25 November 2017

permits any container element
link to other URLs can be retained
mutation observer event detects elements added via JavaScript
minor performance tweaks

v1.0.0, 16 January 2017

Initial commit

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Package last updated on 03 Jul 2020

progressive-image.js