ghostscript ps2ps crops document adding some margins/ borders

Question

I feel noob on this one... But here it comes:

Let's take a Vector program with a PS exporter (with no font sub setting: important to change text dynamically in the future) more specifically the Inkscape version 0.46. Document size A4 and lets draw some lines very close to the border and a simple text, after that you export your ps as noborder.ps:

Everything is really fine! What is on the first lines of postscript file?

%!PS-Adobe-3.0
%%Creator: 0.46
%%Pages: 1
%%Orientation: Portrait
%%BoundingBox: 0 0 596 842
%%HiResBoundingBox: 0 0 596 842
%%DocumentMedia: plain 596 842 0 () ()
%%EndComments
%%Page: 1 1

Now we need to generate a PS file from this PS file (Why? Some new fonts that cannot be uploaded to the printer and dynamically text are changed. PS2PS is a good choice to embed fonts and other elements prior to printing). Let's use ps2ps from ghostscript 8.7.

user@server:/$ ps2ps noborder.ps whyborder.ps

Very good! No errors on running... But... What? BORDERS? MARGINS? CROPPING?

Lets look at the whyborder.ps header:

%!PS-Adobe-3.0
%%Pages: (atend)
%%BoundingBox: 5 6 587 792
%%HiResBoundingBox: 5.000000 6.791406 586.732813 792.000000
%.........................................
%%Creator: GPL Ghostscript 870 (pswrite)
%%CreationDate: 2015/09/09 16:09:24
%%DocumentData: Clean7Bit
%%LanguageLevel: 2
%%EndComments
%%BeginProlog
% This copyright applies to everything between here and the %%EndProlog:

Why is the BoundingBox changed??? Why add borders, margins, cropping? I have tested options like "-dEPScrop", papersize... But the cropping remains... Why???

KenS KenS · Accepted Answer · 2015-09-10T07:25:26

Firstly, stop using an ancient version of Ghostscript! 8.70 is now 6 years old, the current version is 9.16 (shortly to be superceded by 9.18).

Secondly, when experimenting like this do not use a script, use the command line directly. The device being used in the archaic version of GHostscript was pswrite, which was a very poor implementation and only supported level 1 output. The current code uses the ps2write device which is a much more powerful and flexible solution.

Note that in all cases running the input through Ghostscript does not 'embed fonts' or 'edit' or 'compress' the original. What happens is that your input is interpreted to produce graphics primitives which are fed to the device API, the device in question then processes the primitives. For a rendering device this means calling the graphics library to render the primitive to the canvas. For a high level device it means re-emitting the primitive , for example as a PDF operation.

ANY such processing brings inherent risks of approximation, the pswrite device was even worse in that much of the content was rendered to images. So in general it really doesn't embed new fonts, it just embeds pictures of the glyphs. This scales really badly and because the bounding box depends on the resolution can result in signficant inaccuracies.

You should really avoid doing ths unless there is no alternative. If you really must do it, be prepared to accept compromises, do not use archaic versions of Ghostscript and don't use the crappy old pswrite device.

ghostscript ps2ps crops document adding some margins/ borders

2 Answers