TWITCH   amplifies the background of an image by making it, well, twitch. A hyper little (or big, if you like) pinch of distortion scurries about the background, ducking behind the foreground. The background and foreground were differentiated in Photoshop, using magic wand tools and marquees and such to make the mask image shown here. The distortion is all computational.

The original plan and the actual execution for the distortion are sketched below. In the original plan, the twitch fades smoothly into the background because the boundary of the region is pinned down, the center is relocated (rotates around the old center with a variable radius), and the image stretched between them. In the final execution, the image is not continuous across the edge of the distorted area. This produces the glassy, raindrop effect.

You can...
• slow it down or speed it up with the down and up arrow keys
• increase and decrease the size of the disturbance with the left and right arrow keys
• set the stretch of the distortion within that area with number keys 0 to 9 (0% to 90%)

Twitch.html The applet. Twitch.java The source.

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