Featured Image Sharpen Up makes a tiny version of your featured post image and places it in the head of the page. As you scroll down the page, some JavaScript lazy loads the featured images in the background and replaces the tiny images as the full images are loaded.
You may have seen a similar effect used for images on medium.com.
Created on WordPress 4.4, but should work on earlier versions. Tested working on all Twenty Sixteen, Twenty Fifteen, Twenty Fourteen, Twenty Thirteen, Twenty Twelve and Twenty Eleven themes. Should work on other themes, but may need CSS adjustments, depending on theme handling of featured images.
Uses jQuery.Lazy(); (http://jquery.eisbehr.de/lazy/) and Hugh Lashbrooke's plugin template (https://github.com/hlashbrooke/WordPress-Plugin-Template)
Plugin page : Featured Image Sharpen Up plugin @ mabujo
Installing "Featured Image Sharpen Up" can be done either by searching for "Featured Image Sharpen Up" via the "Plugins > Add New" screen in your WordPress dashboard, or by using the following steps:
- Download the plugin via WordPress.org
- Upload the ZIP file through the 'Plugins > Add New > Upload' screen in your WordPress dashboard
- Activate the plugin through the 'Plugins' menu in WordPress
You can also download from GitHub : https://github.com/mabujo/featured-image-sharpen-up/archive/master.zip or composer.