Optical imaging and patterning based on a magnetically controlled ferrofluid

Methods, systems, and apparatus for optical imaging and patterning based on a magnetically controlled ferrofluid are described. One such system includes a substrate and an active region including multiple magnetic field generators. The active region is positioned adjacent to the substrate. The system includes a ferrofluid positioned on the substrate adjacent the active region within a range of a magnetic field of the multiple magnetic field generators. The ferrofluid is distributed across multiple ferrofluid regions. Each magnetic field generator is aligned with a corresponding ferrofluid region.