Turning a MacBook into a touchscreen with $1 of hardware (2018) (anishathalye.com)

A team describes “Project Sistine,” a proof-of-concept that turns a MacBook into a touchscreen using about $1 in parts: a small mirror placed in front of the webcam plus simple computer-vision software. The system detects fingers by analyzing skin-colored regions and their reflection at a sharp angle, then calibrates camera coordinates to screen coordinates using a homography. The prototype converts touch and hover into mouse events and the code is released under the MIT license.