2003.10_Gs, Ps2, Pdf2-Converting File Types.pdf

LINUX USER

gs & PSUtils

Ghostwriter

PostScript is a platform independent programming language that transmits

Simple text files are processed with

a2ps [5]. This program was originally

designed as a conversion tool (text to

PostScript). Later versions of this Post-

Script filter can handle compressed files,

LaTeX documents and even graphic for-

mats (see Figure 1). For a complete

overview of the program’s features, type:

text and images to printers. In addition to the well-known viewers for these

huhn@huhnix:~> a2ps --list= U

delegations

Applications configured for U

delegation

[...]

Delegation `ImageMagick', from U

png to ps

#{del.imagick} 'png:$f' ps:- U

| #{del.psselnup}

[...]

formats there are a number of useful and quick tools for editing and viewing

.ps files in the command line. This article looks into intelligent PostScript pro-

cessing with Ghostscript and the PSUtils.

BY HEIKE JURZIK

G hostscript [1] can handle both

PostScript and PDF files, and

provides numerous drivers

(“devices”) for converting to other for-

mats. Thus, the tool not only offers

printer drivers, but can also convert

PostScript to PDF or process files before

displaying them on screen.

The PSUtils [2] are a collection of pro-

grams for editing PostScript files,

including the following tools psnup

(places multiple pages on a single page),

psresize (changes the page size), psselect

(selects individual pages from a Post-

Script file), pstops (document

manipulation, such as scaling up or

down), psbook (organizes the pages like

in a book), and epsffit (scales an EPS file

to a specific size).

Before we delve into the depths of

command line PostScript processing,

let’s have a look at the basics: What does

the internal format of a PostScript file

look like?

quite common. This format is used to

transport information (mostly images)

between programs and can be embedded

and scaled in other documents. The orig-

inal PostScript code is placed in a

so-called “bounding box” that defines

the horizontal and vertical co-ordinates

and specifies the bottom left and top

right corners of the image.

The Delegation `ImageMagick’, from png

to ps entry indicates that a2ps can use an

external program called ImageMagick to

convert images in PNG format (“Portable

Network Graphics”) to PostScript.

Basics – Part III

There are numerous GUIs for Ghostscript

that allow you to read, convert or print

PostScript, such as Acrobat Reader,

KGhostView, GNOME-GhostView, and

gv . If you need to automate a process (in

a shell script, for example), you can

access the Ghostscript program, gs ,

natively.

Basics – Part II

There are numerous approaches to creat-

ing PostScript and PDF files. If you use

LaTeX [4], you can simply convert .dvi

files to PostScript in the command line:

dvips file.dvi -o .

Box 1: Manual PostScript

Ken Monk’s Website [3] includes a comprehensive tutorial that starts with simple examples (such

as lines and squares), takes you through complex font variants and ends up with numerous tips

and tricks. A simple “Hello World” document would appear as follows:

%!PS-Adobe-1.0 % Version number (PostScript versions 1-3)

/Times-Roman findfont % Find font

48 scalefont % Set font to 48 point

setfont % Make the selected font the current font

100 500 moveto % Set the starting point for text output

(Hello World!) show % Output 'Hello World!'

showpage % Output the current page

Ideally, PostScript files follow rules and conventions to facilitate processing by other programs. For

example, a page description is always split up into a prolog (definitions) and script (which uses

definitions to define the page). In the case of multi-page documents, the individual pages are typ-

ically described independently of one another.

Our simple example demonstrates a few important characteristics:

•Comments start with a percent sign and end with a new line.

• Structure information is a special kind of comment and starts with %! or %% . (Note that these

characters must occur at the beginning of a line, as they are interpreted as “normal” comments

otherwise.)

•PostScript documents always start with %! ,preferably with a version number

Basics – Part I

You could theoretically create a Post-

Script-File manually, just using an editor

(see Box 1), as the format is pure ASCII.

But this task is normally performed by

the print routine of a program. Devices

that process information in PostScript

files need to have a PostScript inter-

preter, in order to output the file on

screen or to a printer – this device could

be a PostScript printer that uses a

firmware based PostScript interpreter.

In addition to .ps files, .eps files

(“Encapsulated PostScript”), are also

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Command Line: gs & PSUtils

gs & PSUtils

LINUX USER

You can additionally specify the page size

– either by stipulating the dimensions, as

in -wWidth and -hHeight (the program

can handle either point or centimetre

units), or set the -p flag and specify a

well-known format a3, a4, a5 etc.

As the name would suggest, the psre-

size tool changes the page format. If the

file is in a European format, such as

<A4>, you can use the following syn-

tax to convert it

psresize -PA4 -pletter file.ps U

new_file.ps

Figure 2: Different quality – ps2ascii vs. pstotext

psselect extracts specific pages – for

example, you can use the -e flag to

extract pages with even numbers, or -o

for odd numbers. This is useful if you

need to print both sides of the sheet: If

you have a laser printer, you could print

all the even pages first, then re-insert the

stack of paper and print all the odd

pages. The -p1,2,3,4 syntax allows you to

specify the pages you need as a comma-

separated list, which can include blocks

of several pages, for example

gs can be launched on the command

line with or without a PostScript or PDF

file as a parameter. Besides a display

window, you will also see output such as

the following in your terminal window:

tribution: the current “AFPL Ghostscript”

version is 8.10).

To use a specific driver (device), spec-

ify the device as a parameter when

calling gs , for example, -sDEVICE=epson

file.ps , if you want to output the file on

an Epson printer, or -sDEVICE=x11

file.ps to output the file on screen. Alter-

natively, launch gs and enter the

following at the prompt:

huhn@huhnix:~> gs abc.ps

ESP Ghostscript 7.05 U

(2003-02-05)

[...]

Loading NimbusRomNo9L-Regu font U

from /usr/share/ghostscript/ U

fonts/n021003l.pfb... 2052880 U

687555 1642520 342518 0 done.

[...]

>>showpage, press <return> to U

continue<<

psselect -p1-5,7-9 abc.ps new.ps

huhn@huhnix:~> gs

[...]

GS> (x11) selectdevice

GS> (abc.ps) run

But there is no need to decipher complex

instructions, just to quickly view a Post-

Script file – ps2ascii outputs the

document in cleartext format (see Figure

2). pstotext is another tool that fulfills

the same task, but achieves better

results. ps2ascii is included with the

Ghostscript package, and pstotext is

available from [6].

If you do not want to print the file

directly, you can use the -sOutputFile

option instead: gs is capable of creating

images from PostScript files. The driver

list includes a jpg option, for example.

The following syntax:

If you press [Return] at this point, or

launch gs without specifying a filename,

the GS> prompt is displayed. You can

quite the interpreter by typing quit , or by

pressing [Ctrl-C]. gs -h or gs -? displays

the help text, which includes an

overview of a few drivers and Ghost-

script switches, plus the version number

(GNU Ghostscript is currently at version

7.05.6.

There is another fork, released under

a more restrictive license, although it

basically only restricts commercial dis-

INFO

huhn@huhnix:~> gs -sDEVICE=jpeg U

-sOutputFile=abc.jpg abc.ps

[1] Ghostscript:

http://www.cs.wisc.edu/~ghost/

[2] PSUtils: ftp://ftp.dcs.ed.ac.uk/pub/ajcd/

psutils.tar.gz

[3] PostScript Tutorial by Ken Monk:

http://www.mis.coventry.ac.uk/~kenmk/

pstut/psindex.htm

[4] LaTeX: Heike Jurzik, LaTeX Workshop:

www.linux-magazine.com/issue/26/

LaTeX_Part1.pdf

www.linux-magazine.com/issue/28/

LaTeX_Workshop_Part2.pdf

[5] a2ps:

http://www.infres.enst.fr/~demaille/a2ps/

[6] pstotext: http://www.research.compaq.

com/SRC/virtualpaper/pstotext.html

converts a PostScript document called

abc.ps to a JPEG file called abc.jpg .

Miscellaneous Tools

The PSUtils package contains a number

of utilities for processing and re-format-

ting PostScript files. The psnup tool

allows you to place several document

pages on a single page, for example:

GLOSSARY

dvi file :When LaTeX runs (“latex file.tex”) it

creates numerous files in a directory for fur-

ther processing. These include a file with the

“.dvi” (device independent) suffix. This is a

device independent output file that can be

used for screen or printer output, provided

you supply an appropriate driver.

huhn@huhnix:~> psnup -2 file.ps U

2page_file.ps

[1] [2] [3] [4] [5] Wrote 5 U

pages, 464732 bytes

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October 2003

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