HP 4 FAMILY - Manual (Page 50)

Transparency Modes: The white pixels of the source and/or
pattern may be made transparent (source transparency 0,
pattern transparency 0). The destination shows through
these areas.
Transparency modes are set by the Source Transparency
(?*v#N) and Pattern Transparency (?*v#O) commands
(refer to the PCL 5 Printer Language Technical Reference
Manual).
The print model allows logical operations, such as AND,
OR, XOR, NOT, to be performed on source, texture, and
destination images. Transparency modes and Logical
Operation must be specified before printable data is sent.
Operators
Source Transparency (specified before logical operation;
default is transparent)
Pattern Transparency (specified before logical operation;
default is transparent)
Logical Operators (default is Texture OR Source)
Operands
Source objects: character cell, raster image, rule,
HP-GL/2 vectors and polygons
Texture: pattern mask
Destination: current page definition
Assuming three bits per pixel, the following diagram shows
the print model process.
2-14 Printer-Specific Differences