The acrylic ink we use is available in dozens of colors, which opens up interesting computational challenges to adjust for color in addition to stipple positions. This artwork is a colored cartoon print of the joker, done in three drawing passes each using a different colored ink.
Stippling with aerial robots project page for the publication at Computational Aesthetics / Expressive.
This video produced by the McGill University newsroom provides a high level overview of the project.
The supplementary video for the conference publication, showing time lapse videos of various portraits being created (creation of The Joker not shown).