Reverse engineering is a powerful tool for duplicating real objects from data acquired by tracking systems, industrial X-ray computed tomography (CT), laser scanners, and image captures. This work proposed a novel method using the three-dimensional (3D) reconstruction and 3D printing to duplicate a mechanical key based on only one single naturally-captured photograph. A reverse engineering system of the mechanical key was self-developed which includes functions of projective transformation, curve extraction, point clouds generation, and 3D geometry reconstruction. The database technology was i...