Provided is print engine controller of a printhead assembly having a plurality of printhead modules. The controller includes a memory buffer to receive rasterized page data from a computer system, a page image expander for expanding the page data to retrieve page images, and dithering means for dithering a continuous tone (“contone”) layer over the page data. The controller also includes a compositor for compositing a black bi-level layer of the contone layer, rendering means for rendering infra-red tags over the contone layer, and an output driving the printhead modules to print the composited page data.