Multi-resolution images

New in Tiki18. PluginImg has a new option called 'retina'. If you have a fixed width image, it will pull up a 2x version of the image for users with retina display (and 1x for users who don't). Note: source needs to be at least 2x the size of the width of the image being displayed.

More advanced (see video and/or read up on srcset and sizes attributes for html image tags):
Added 'widths' and 'sizes' options to be able to serve up responsive images that change in size depending on how the image
is displaying in the browser.