UNIDRV Does Not Send Black Plane to Dump() Function

• Microsoft Windows Device Driver Kit (DDK) for Windows, version 3.1

If a minidriver implements its own Dump() function, it must handle black extraction in that function.

UNIDRV.DLL does not create a separate black plane in the PDEVICE structure that is passed to the Dump() function. UNIDRV processes the output for a three- and four-color printer exactly the same until it reaches the Dump() function. If the DC_EXTRACT_BLACK bit is set in UNITOOL and the number of color planes is set to 4, then UNIDRV will extract the black plane in its own Dump() function.

This extraction is performed by removing black bits from (r,g,b) planes and putting them in the black plane. For every bit, (r,g,b) is checked to determine whether it is (0,0,0) (black). If true, that bit is set in the black plane, and cleared in (r,g,b).