Adaptive Image Styles
As of version 1.5, AIS works with Drupal 7.20 or better.
This module allows any image to be adaptive simply by setting it to be rendered with the 'adaptive' image style. This module also integrates with the Media module, and adds an adaptive option selectable from the media displays.
This module also works with inline images and WYSIWYG making it almost trivial to add adaptive image support to your existing site.
Which image styles are used to generate the adapted images is also configurable.
The adaptive image styles module offers an easy way to make any images adaptive. Since this module intergrates with Image Styles in Drupal core, the images are resized server-side and you can use your existing image styles as target sizes/styles to be adapted to.
Simply choosing to display the image with the "adaptive" image style with make the image adapt to the clients window width. The Adaptive Image Styles administration page provides an interface for choosing which image styles are using to generate the adapted images and set the threshold for when they are chosen. The threshold refers to browser window width.