HP PCL/PJL reference (PCL 5 Printer Language) - Technical Reference Manual Part I

EN Introduction 13-3
Pattern Transparency Mode
The transparency or opaqueness of the white pixels in the pattern.
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.
Figure 13-2 Opaque and Transparency Modes
Figure 13-3 illustrates the effects of the source and pattern
transparency modes on the final image.
In the first example (1a), the transparency mode for both the source
image and the pattern is transparent. Since the source mode is
“transparent,” only the black-pixeled region (the circle) of the source
image is overlaid on the destination. Since the pattern mode is also
transparent, the patterned source image is applied only to the white
areas of the destination image.
In the second example (1b), the source mode is still “transparent,”
but the pattern mode is “opaque” — so the pattern’s white pixels are
applied to the destination. The resulting image shows the entire circle
region visible and patterned.
In the third example (1c), the source mode is “opaque” and the
pattern mode is transparent. Since the source mode is opaque, the
entire source image (the circle and the surrounding square) appears
overlaid onto the destination. The pattern, however, is allowed to pour
through only onto the white-pixeled area of the destination. The circle
is visible in the result, but only two opposing quarters appeared
patterned.
In the fourth example (1d), both source and pattern modes are
“opaque.” The entire source image is overlaid onto the destination,
and the entire circle is patterned.