It is necessary that paper be moved past the printhead at a constant
velocity to obtain artifact-free printing. Therefore the printhead
requires a constant stream of data during printing. Whilst it is possible
to rasterize the page using a page description language directly to the
printhead, it is uneconomical. Hence the redering is carried out in the
PC. However, the standard USB peripheral connection is the standard
connection on PCs, which places a constraint on the limit of data per
page that can be transmitted to the printer and still obtain a reasonable
rate of printing. Thus the contone images and graphics are rendered in
the PC to a pixel level, and the black text and graphics are rendered in
the PC to a dot level, where the rendered data is compressed and
transmitted to the printer. The transmitted data is decompressed and
combined and the images overlaid and printed.