Tips for Manipulating Postscript

Translating postscript files from A4 to US Letter format

Unfortunately, the majority of our documents are in A4 format, while many of our collaborators must use US Letter printers. Here are some ways to translate files from one format to the other:

If you have the psresize utility available, it works very well:
```
	psresize -PA4 -pletter a4file.ps letterfile.ps
```
If not, then ...
If you have a sufficiently advanced version of the psnup program on your machine, this will work:
```
	psnup -pletter -Pa4 a4file.ps letterfile.ps
```
This scales the A4 text down by 0.94, and applies a small horizontal shift of 7 points. If psnup fails for you, the same transformation can be accomplished using pstops:
```
	pstops '0.94@1(7,0)' a4file.ps letterfile.ps
```
If that also fails, you can use the following simple perl script: a4toletter. You use it like this:
```
	a4toletter a4file.ps letterfile.ps
```
According to Andy, almost all A4 documents merely require a downward translation by 25 points to be printable on US Letter paper. As long as the text doesn't stray too close to the margins, this solution avoids the 6% loss in type size caused by the previous method. Again, the y shift can be done with pstops:
```
	pstops '0@1(0,-25)' a4file.ps letterfile.ps
```
or with a perl script: a4toletter-shift. Once more, usage looks like this:
```
	a4toletter-shift a4file.ps letterfile.ps
```

Extracting figures from postscript files

Postscript files which include figures actually preserve the source of the original eps files intact. You can easily extract the figures ... they are framed by two distinctive lines in the ps file:

	%%BeginDocument
	...
	%%EndDocument

You can extract the eps files by hand in a text editor. Note, however, that the bounding box for the eps figure is lost. (Well, not exactly, but it's a bit complicated to pull it out, and I haven't verified a robust method yet). The easiest thing to do is to simply run ps2epsi on the code you extracted ... it will make the bounding box for you, and insert the usual eps header lines.

Here is a perl script which does all this automatically for you: extract-eps. Basically, you type

	extract-eps file.ps

and all embedded eps files will be extracted (using their original filenames). Type

	extract-eps -h

to learn about a few command line options that are available.

Changing colour postscript to black-and-white

If often happens that you have a lovely colour figure that you would like to render in black-and-white ... for example, a plot that you showed at a talk, but must now include in a printed proceeding. If you don't have a B&W version of the plot at hand, you can convert your colour file. The two simplest choices are:

Take the RGB (red-green-blue) specification of each colour, average the values, and use that as a grayscale setting.
Turn all colours (and any grayscales) to black.

The second option is perhaps better for plots, while the first is more suitable for figures and diagrams. It depends a lot on the particulars of your colour file.

Here is a perl script which performs either of these manipulations: bw_convert. The usage syntax is

	bw_convert [-b] colour-file.ps bw-file.ps

The -b option engages procedure #2 above -- convert all colours and greys to black. Otherwise, procedure #1 is used.

About the perl scripts

After you download the little scripts, you must of course do chmod a+x before they will run. :-)

The Quest for Wizardry

Postscript is a programming language, just like FORTRAN, C, or PERL. Postscript files are in ASCII text, just like any other source code, and so can be readily hacked ... if you know the language. :-) In fact, it is a rather nice language, extremely similar to that of an RPN calculator -- if you have ever used such a calculator, the syntax of postscript will be perfectly intuitive to you. Here are 4 links that can take you all the way from Acolyte to Wizard:

A First Guide to Postscript, by Peter J. Weingartner, is the ideal place to start. It is brief, extremely well written, and teaches you about 95% of what you need to know to be a consummate ps hacker. One little tip: when you start hacking ps files, be aware that almost all programs that write postscript (e.g. dvips or fig2dev) insert a lengthy header containing numerous definitions. If you start hunting around through the meat of a ps file, and find that you recognize none of the commands, it's simply because they were all defined (or redefined) at the beginning of the file (with a shorter name, if nothing else).
Paul Bourke's PostScript Tutorial is the next thing to read. It is much more brief than the previous document, but adds information about a couple of useful things, like coloured inks.
Now you have all the fundamentals under your belt, and you need a quick reference. Bookmark this: the Luminous Postscript Index. Happily for us, Mr. Milanek has copied the famous index from Luminous Corp (which seems to have vanished) to a computer in Czechoslovakia.
Do you have access to a printer where you can dump 900+ pages and not (a) go through $200 worth of inkjet cartridges or (b) incur the eternal wrath of your colleagues? If so, you may achieve Complete Mastery of postscript by downloading the Encyclopedia itself from the horse's mouth: the celebrated `Red-and-White Book', also known as the PostScript Language Reference, may be retrieved for free from Adobe.

Maintained by N.C.R. Makins (makins@uiuc.edu)