[bug-gs] colours & encapsulated eps files

[Dan Coby]

>If this isn't a bug that developed sometime after 7.04, then any
>comments or suggestions about how to preserve the colours would
>be appreciated.

Actually the result that you are seeing is the result of 'preserving'
the colors.

Between 7.04 and 8.53 the handling of color spaces in PDF output
was 'improved'.  In 7.04 most color spaces were converted to the
process color model of the pdfwrite device.  The default process
color model for the pdfwrite device is DeviceRGB.  Thus, in 7.04,
most color spaces were converted to RGB.  In 8.53, the operation
of the pdfwrite device was changed to keep the original
color spaces specified in the input document.  Thus if the input
file specified a CMYK color, then the output PDF file contains
a CMYK color.

This brings the next question:  Why do the colors look different?
Adobe Acrobat and Adobe Reader apply a default color management
profile to all PDF files when displaying PDF files.  The default
profiles for CMYK color spaces make CMYK color spaces look darker.
This is an attempt to simulate the appearance that is obtained
with real inks on a real printer.  If the application that created
the PS file is creating CMYK color spaces in the PS file, then
there can be (and often is) a difference in appearance between
the colors displayed in the original application and the appearance
in Acrobat or Reader.

One way that may avoid this problem is to not use CMYK color spaces.


Dan


-----Original Message-----
From: bug-gs-bounces at ghostscript.com
[mailto:bug-gs-bounces at ghostscript.com]On Behalf Of David Pike
Sent: Tuesday, January 03, 2006 10:01 AM
To: bug-gs at ghostscript.com
Subject: [bug-gs] colours & encapsulated eps files 



Hi all.

This may or may not be a bug.  The situation I'm in is that I have a
latex document with an encapsulated postscript diagram.  The eps file
has colours and appears to use the CMYK format for them.

AFPL ghostscript/ps2pdf 7.04 converts the .ps file generated by latex
and dvips to a pretty PDF file with no problem.

AFPL ghostscript/ps2pdf 8.53, however, produces a PDF file in which
the colours in the diagram appear to have faded or lost their lustre.
I've tried specifying a number of options for ps2pdf to try to get
the desired effect (ie to keep the colours as they were in the
original postscript file) but I am having no luck.  Sample files
that illustrate what I'm experiencing are available at:

http://www.math.mun.ca/~dapike/trial.ps
http://www.math.mun.ca/~dapike/trial.pdf  (this is from 8.53)

If this isn't a bug that developed sometime after 7.04, then any
comments or suggestions about how to preserve the colours would
be appreciated.  

Thanks,

- David.


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