The FilterGraphics function prepares a buffer of raster data (which it re-ceives from the Universal Printer Driver) for rendering on the printer. The
FilterGraphics function is necessary if a printer does not process graphics
data in the manner supported by the Universal Printer Driver. For example,
when the Universal Printer Driver passes a byte of raster data to a 9-pin dot-matrix printer, it orders the individual bits so that bit 7 corresponds to the top-most pin and bit 0 corresponds to the bottom-most pin. If a given printer ad-dresses pins in a different format, it must provide a FilterGraphics function
to correctly order the bits in each byte of data.