Oliver Heins schrieb:

Peter Rolf <indiego@gmx.net> writes:

Oliver Heins schrieb:

Yes, I noticed that, too.  But to me it looks like it is first knocked
out in the pdf, and then the overprint flag is set.

Good point. In that case the text must be set twice, as knockout and
overprint can't coexist. I have looked into the uncompressed mkii PDF
(\nopdfcompression) and I can not see any obvious flaw. The parts are
clearly separeted by '/GSknockout gs' and '/GSoverprint gs', the black
text is not set twice.

Just an idea: the colorspace of the picture is RGB, the text is set in
CMYK. Maybe the mixed color spaces mess up things here.


But shouldn't the same effect be seen with other colors than black then,
too?  And it only happens with black, and I think it happens even when
you do it within a cmyk-only document:

I get the same 'kind of knockedout' text as in the other example...
but the black text is set as /DeviceGray and not /DeviceCMYK (k-component). You can make this visible by using
'Vorschau: Separiert' with the option 'Einblenden: Nicht-DeviceCMYK'.

I think this is just a limitation of the previewer. You can define your own cmyk black with \definecolor[myblack][k=1]. I bet that the knockedout effect will vanish with cmyk black (untested).

Can you test the following?  My Acrobat is on a machine without net, and
my usb stick broke within the experiments.

prepress mess + bad luck => *have a break and enjoy your weekend* :)

Best regards,
 olli

\setupcolors[state=start, cmyk=yes, rgb=no]

\starttext

{\bfb\setstrut
\startoverprint
\framed
[background=color,backgroundcolor=magenta,
foregroundcolor=yellow,align={lohi,middle},
frame=off,width=3.5cm,height=3cm]
{overprint\\\property[knockout]{knockout}}%
\stopoverprint
\framed
[background=color,backgroundcolor=magenta,
foregroundcolor=yellow,align={lohi,middle},
frame=off,width=3.5cm,height=3cm]
{knockout\\\property[overprint]{overprint}}}%

{\bfb\setstrut
\startoverprint
\framed
[background=color,backgroundcolor=magenta,
foregroundcolor=black,align={lohi,middle},
frame=off,width=3.5cm,height=3cm]
{overprint\\\property[knockout]{knockout}}%
\stopoverprint
\framed
[background=color,backgroundcolor=magenta,
foregroundcolor=black,align={lohi,middle},
frame=off,width=3.5cm,height=3cm]
{knockout\\\property[overprint]{overprint}}}%

\stoptext