Move pointer over the lower image. As you move the mouse, the left side of the image is unfiltered, the right side is Differnce of Gaussians result. As you move the mouse up and down on the image you change the sigma parameter of the gaussians.
(This implementation is based on the work of https://www.shadertoy.com/view/4dfGDH#.)
Check out the source code.This demo uses WebGL. Not all devices and browsers are supported.