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List:       imagemagick-user
Subject:    Re: [magick-users] PostScript-Bug in IM 6.3.1?
From:       Anthony Thyssen <anthony () griffith ! edu ! au>
Date:       2006-12-11 2:04:28
Message-ID: 200612110204.kBB24Skv004774 () wraith ! its ! griffith ! edu ! au
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Hugemann on  wrote...
| In my e-mail from 6th of December, I announced the following solution to 
| get a transparent canvas when converting a vector EPS file:
| 
| convert -density 300 -channel RGBA logo.eps logo.png
| 
| (And, yes, I took this somewhere from Anthony's website.)
| 
| When trying to share this solution with others, I ran into trouble as 
| this seemed to work only on the very computer I was working on. After 
| hours of research work I could finally nail the problem down:
| 
| The above works with IM version 6.2.5, but not with the current version 
| 6.3.1!
| 
| I am working on Windows machines and using GPL GhostScript 8.15. I 
| installed IM from the standard Windows Installer packages
| 
| ImageMagick-6.2.5-5-Q8-windows-dll.exe
| and
| ImageMagick-6.3.1-0-Q16-windows-dll.exe
| 
| ...............
| 
| But there are questions left: How does IM know what PostScript delegate 
| to use and what program path to use? In the configuration file 
| delegates.xml the generic name @PSDelegate@ is used. You can find out 
| about the PS delegate by typing
| 
| identify -verbose test.eps
| 
| because the PS delegate is listed at the end. But I could not identify 
| but what strategy IM finds out about the PS delegate.
| 
| Wolfgang Hugemann
| 
Make sure the postscript header line
   %%LanguageLevel: 3
is present in the postscript image...

In IM examples I do this with a quick perl hack...

  perl -pe 'print "%%LanguageLevel: 3\n" if 2..2' image.ps  image_new.ps

The note for this reads...

=======8<--------
The "perl" command in the above example adds a '%%LanguageLevel: 3' line
to the generated postscript file. This is needed so that the later
transparent postscript options to work correctly.

The real problem here is that Ghostscript does not provide a single
conversion method for IM to use, requiring IM to try and figure out
correct call style to use to generate a correct image for the given
postscript.
=======8<--------

If I did not add this line the IM Examples   'RGBA' transparent postscript
also fails.

Mind you it also presents another way of converting a non-transparent
postscript to a transparency (like an overhead transparency), though
that many not be want you want.  :-)


There has also been discussions on the IM Discourse forums, that talk
about adding some user defined poscript delegates for special handling
of transparencys, for special cases.  these may be of relevence to you.



  Anthony Thyssen ( System Programmer )    <A.Thyssen@griffith.edu.au>
 -----------------------------------------------------------------------------
  "Where's the kaboom? There was supposed to be an EARTH-shattering kaboom!"
                                                        -- Marvin Martin
 -----------------------------------------------------------------------------
     Anthony's Home is his Castle     http://www.cit.gu.edu.au/~anthony/
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