Re: Bug with overprinting in Mark II/IV?

[Peter Rolf <indiego@gmx.net>]

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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
>
>
>   


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