Sometimes PDF output from an application (for instance, a web browser) has text
in colors which would not print well on a grayscale printer. The
BlackText operation blackens all text on the given pages so it will be
readable when printed. This will not work on text which has been converted to
outlines, nor on text which is part of a form.
The BlackLines function does the same for lines and BlackFills
for fill colors.
![\begin{framed}
\noindent\textit{Blacken lines in a document}
\par
\vspace{2mm}
\...
...l\verb!Cpdflib.BlackLines(pdf)!
\end{minipage}\\ [5mm]
\end{tabular}\end{framed}](img88.png)
Quite often, applications will use very thin lines, or even the value of 0,
which in PDF means "The thinnest possible line on the output device". This
might be fine for on-screen work, but when printed on a high resolution device,
such as by a commercial printer, they may be too faint, or disappear
altogether. The ThinLines function prevents this by changing all lines
thinner than the given minimal thickness to the given width. For example:
![\begin{framed}
\noindent\textit{Thicken lines to at least 2pt}
\par
\vspace{2mm}...
...es(pdf, Cpdflib.All(pdf), 2.0)!
\end{minipage}\\ [5mm]
\end{tabular}\end{framed}](img89.png)