Ghostscript:
Taking PDF Creation to the Next Level
Copyright (C) 2007 by Steve Litt, All rights reserved. Material
provided as-is, use at your own risk.
Contents
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Other PDF Related Pages
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Disclaimer
This page is an introduction to ghostscript -- not an authoritative text. This
page may have errors -- in fact it probably does. DO NOT trust what you
see on this page without verifying it for yourself. I am not
responsible
for any damage or injury caused by your use of this document, or caused
by errors and/or omissions in this document. If that's not acceptable
to
you, you may not use this document. By using this document you are
accepting this disclaimer.
Introduction
There's a program called ps2pdf that's very easy to use:
ps2pdf mydocument.ps
Easy, clean, fast. But sometimes not enough.
Perhaps you need to make a landscape PDF from a postscript file lacking
the proper orientation cues. Sounds easy, but it can be ruinously
difficult, requiring ghostscript (gs). Or perhaps you need to create a multipage PDF from several single page source files. Once again, gv to the rescue.
Viewing Device Names
Ghostscript uses various devices to accomplish its magic. Some devices
are printer drivers, while others print to specialized files (there's a
PDF device). Here's how you see all the device names, in alphabetical
order:
echo 'devicenames == ' | gs -q | tr " " "\n" | sort
The preceding pipes the command 'devicenames ==' into the ghostview interpreter with the -q
(quiet) switch, assuring that only device names are output. The
interpreter's output is all devices on a single line, which of course
isn't what you want, so you split it into multiple lines with the tr command, and then sort the lines with the sort command.
Once you've viewed the list of devices, you're in a much better position to know what to do. In my case, I use the device named /pdfwrite to write PDFs (whoda thunkit?).
Viewing Paper Sizes
You'll need paper sizes for some ghostscript (gv)
commands. The following script (let's call it papersizes.sh) reads a
.ppd file and outputs a list of all paper size names and their sizes.
The .ppd file will probably be on your system, so use the following
command to locate it:
locate -r \.ppd$ | grep -i pdf
In my case, the preceding command returned a single file, /usr/share/ghostscript/8.15/lib/ghostpdf.ppd. You will use this filename to set a variable in the script, which follows:
#!/bin/bash
pdfppd=/usr/share/ghostscript/8.15/lib/ghostpdf.ppd
grep ^*PageSize $pdfppd | cut -d " " -f 2-10 \
| sed -e "s/:[^\[]*/ : /" \
| sed -e "s/\].*/]/"
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Obviously, you'll change your $pdfppd variable to reflect the file on your system. If you can't find one, you can download this file.,
or if that file no longer exists when you read this paper, perform a
Google search on the terms ghostscript, A4 A3 Letter and Legal without
quotes. That should bring you a suitable .ppd file, which you can
download.
Running the preceding script lists all paper size names followed by a
space and colon, followed by a width/length pair of dimensions in
points (there are 72 Postscript points per inch). The two dimensions
are enclosed in square brackets, separated by a space, which is how you
use them in a ghostscript command. Remember, if you want to specify
landscape, you switch the two dimensions.
Making a Simple PDF from a Portrait Postscript File
If you have a file called myfile.ps, here's how you convert it into a PDF called myfile.pdf:
gs -sDEVICE=pdfwrite -sOutputFile=myfile.pdf -dBATCH -dNOPAUSE myfile.ps
This is a pretty complex command, so here's the explanation:
gs
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The ghostscript program |
-sDEVICE=pdfwrite
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Write a PDF |
-sOutputFile=myfile.pdf
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Name the output file myfile.pdf |
-dBATCH
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Exit the interpreter upon processing of the last file. Otherwise you'd end up in the Ghostscript environment. |
-dNOPAUSE
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Do not wait for user input, but instead just execute the commands |
myfile.ps
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The postscript file to convert |
Making a Landscape PDF
The difficulty of making a landscape PDF file depends on the postscript
file from which it comes. Correctly made landscape postscript files can
be converted with the ps2pdf
program. However, if the postscript file doesn't contain the necessary
orientation cues, even though the postscript file is viewable and
printable as landscape, the resulting PDF looks like a landscape
drawing on a portrait paper, with the rightmost area of the image cut off. When this
happens, you have four choices:
- Find a different way to convert the source to postscript
- Convert the source directly to PDF
- Hand tweak the PDF with an editor or other tool (pdftk?)
- Use ghostscript
Obviously the first two alternatives are the best and easiest, but
sometimes they're not available. As far as the third, good luck with
that, because after an hour of trying I gave up trying to correct the
postscript file with Vim.
If you cannot directly convert source to PDF, and your postscript or
encapsulated postscript file won't create a landscape PDF, then you'll
need to use ghostscript to twist the paper without twisting the
image. There are two ways to strongarm an unwilling .ps file into a
landscape PDF:
- Leave the paper portrait and twist the image. Therefore, when you
look at it on the screen, the image is sideways, but printing it
portrait will do exactly what you want.
- Make the paper landscape and leave the image alone. This makes
the on-screen image exactly what you want, and is the best for
projector presentations, but from what I've read it can have some
unpleasant surprises when printed.
Let's look at how you do each of these alternatives:
Twist the Image
Once again, this is great for printing but you'll need to turn your
head 90 degrees to correctly view it on the screen. Here's the command:
gs -dBATCH -dNOPAUSE -sOutputFile=myfile.pdf -sDEVICE=pdfwrite -dAutoRotatePages=/None \
-c "<< /PageSize [612 792] /Orientation 3 >> setpagedevice" 90 rotate 0 -612 translate -f myfile.eps
Make the Paper Landscape
The preceding method was wonderful from a printing perspective, but
you'll need to turn your head 90 degrees to correctly view it on the
screen. For a PDF that looks great on the screen, especially for
presentations, you leave the image orientation alone and make the paper
landscape. Here's how it'd done:
gs -dBATCH -dNOPAUSE -sOutputFile=myfile.pdf -sDEVICE=pdfwrite \
-c "<< /PageSize [792 612] >> setpagedevice" -f myfile.eps
Making a Multipage PDF From Multiple .ps or .pdf Files
Ghostview can't work miracles. All the pages must be the same
orientation, and must match in some other ways. In an ideal world, all
source pages would be made in the same way with the same application.
For instance, let's say you created four separate portrait Gimp
drawings and exported each to an .eps file. Here's how you might merge
them into one:
gs -sDEVICE=pdfwrite -sOutputFile=myfile.pdf -f myfile1.eps myfile2.eps myfile3.eps myfile4.eps
If all the drawings were landscape in source, but one or more have the
problem of converting to portrait in ps2pdf, then you need to strongarm
the paper orientation while leaving the image orientation alone:
gs -sDEVICE=pdfwrite -sOutputFile=myfile.pdf -c "<< /PageSize [792 612] >> setpagedevice" -f myfile1.eps myfile2.eps myfile3.eps myfile4.eps
If you have four "similar enough" PDF files but don't have the source
to them, you can combine them by using PDF files as building blocks:
gs -sDEVICE=pdfwrite -sOutputFile=myfile.pdf -f myfile1.pdf myfile2.pdf myfile3.pdf myfile4.pdf
Other Uses of Ghostscript
Ghostscript has many devices besides pdfwrite. There's a device to
write .png files, another to write .pnm files, several for .tiff files,
one for .xcf files, a few for .bmp files, .cif files, and cups
printing. There even appear to be fax related outputs. In addition to
this, you can create printer files for many, though certainly not all,
popular printers.
Summary
For simplicity, it's best to either export from source directly to
.pdf, or if that's not possible or practical, from source to .ps or
.eps and then use ps2pdf.
But when the going get tough, the tough use Ghostscript to do those
unusual tasks like creating landscape .pdfs from unruly postscript
files, and creating multipage .pdfs from source apps not supporting
multipage documents.