ImageGear for C and C++ on Windows v19.1 - Updated
Mosaic Effects
User Guide > How to Work with... > Image Processing and Cleanup > Special Effects > Mosaic Effects

ImageGear provides the following mosaic effects:

See also IG_FX_pointillist in the Artistic Effects section.

Original

Pixelate Effect

Tile Mosaic Effect - Square

Tile Mosaic Effect - Spider's Web