thresholdMirror: video sensing

I created a mirror that only shows change in brightness from frame to frame. The mirror is initially set to a neutral grey color, if a pixel from the incoming video is brighter than the corresponding pixel from the previous frame, the difference is added to grey and that pixel on the mirror becomes brighter. If a pixel from the incoming video is darker than the corresponding pixel from the last frame, the difference is subtracted from grey and that pixel on the mirror becomes darker. If the there is no change in brightness between the current video pixel and the previous video pixel, the mirror remains grey. The final effect is a mirror that only reflects change. The mirror is inherently interactive; if a person stands still in front of the mirror they disappear, slight motions shows a ghostly refection, while vigorous movement reflects a much more defined shape.