HP L 5 manual Opaque and Transparency Modes

•Pattern Transparency Mode—The transparency or opaqueness of the “white pixels” in the pattern (see the note below). When set to 0 (transparent), these pixels have no effect on the destination; when set to 1 (opaque), they are applied through the black pixels of the source pattern to the destination.

•Logical Operations—the Print Model uses logical operations, such as AND, OR, XOR, and NOT when determining which bits of the source, pattern, and texture become part of the resulting image. The Logical Operations command (?*l#O) can vary the logical operation used, thus varying the outcome.

Note	For RGB color images, “white” pixels are those for which all color
	primaries are 255. For CMY color images, “white” pixels are those for
	which all color primaries are 0.
	For all rendering algorithms, white dots introduced in the dithering
	process are not subject to transparency modes.
	Figure 5-2 illustrates the effects of the source and pattern
	transparency modes on the final image. (The transparency modes
	work a little differently with rectangular area fill—see “Pattern
	Transparency for Rectangular Area Fill” near the end of this chapter.)

This example uses the default ROP. The output may appear differently depending on the colors used.

Figure 5-2 Opaque and Transparency Modes

EN The PCL Print Model 5-3