Xerox DocuColor 2060, Troubleshooting Manual, Page: 46 / 60

Optimizing print quality
5-4 Troubleshooting Guide
If either of the above procedures is successful, the transfer
functions return the same color levels that are passed to them
without modifying or mapping the level. On printers which do not
allow the overwriting of the transfer function, the settransfer
operator does not affect the mapping of gray values between the
output of the print device and specified levels of color.
NOTE: Settransfer actually sets the transfer functions for all
four color components (red, green, blue, and gray) to the same
value. The setcolortransfer operator sets the transfer functions
individually.
Smooth curves—setflat
PostScript masters that use the PostScript operator setflat
produce inconsistent output across different PostScript printers.
setflat controls curve rendering smoothness. PostScript curve
operators use cubic Bezier control points to define the curve
shape. These curves can be rendered from straight line
segments. Normally the line segments are so short that the
curve appears smooth. The setflat operator indirectly controls
the length of the straight line segments. As stated in the
PostScript Language Reference Manual, second edition, “If the
flatness parameter is large enough to cause visible straight line
segments to appear, the result is unpredictable. Setflat sets a
graphics state parameter whose effect is device-dependent. It
should not be used in a page description that is intended to be
device-independent.”
Invisible strokes—0 setlinewidth
PostScript masters that use the PostScript operator setlinewidth
are not consistent across different PostScript printers.
setlinewidth controls the width of a stroked line. When
setlinewidth is executed with an input of zero, it produces a line
that is one pixel wide. On devices whose dot size is small, single-
pixel-width lines may be invisible.
Scan conversion—fill, eofill, and stroke
Scan conversion algorithms are implementation-dependent, so
different PostScript printers paint (“turn on”) different dots,
resulting in output differences. For filled circles, PostScript
printers differ in the dots they paint at the edge of the circle; thus,
some printers produce slightly larger circles than others. For
large circles this is not noticeable, but for small circles, it is.