[gs-devel] Converting pdf to eps

[Yang]

Ralph Giles giles-at-ghostscript.com |ghostscript| wrote:
> On Tue, Dec 11, 2007 at 03:47:14PM -0500, Yang wrote:
> 
>> ps2pdf: uses gs to produce postscript-3; results are terrible
> 
> I think you mean this produces PDF? We don't have a Postscript level 3 
> output device.

Actually, I meant pdf2ps.

I just assumed that the ps files generated by pdf2ps and convert were in 
Postscript-3 since they begin with "PS-Adobe-3.0")

> 
>> convert: identical to ps2pdf
> 
> I believe convert just calls ghostscript, so that is to be expected.

Yeah, ImageMagick uses ghostscript, but I just wanted to point out that 
the results are identical (which is not necessarily implied by the 
former statement).

> 
>> ps2ps2: uses gs to produce postscript-2; for some files, the result 
>> cannot be viewed in evince (errors); so far have always been able to 
>> view in gs or display; seems to yield high quality as well
> 
> Ghostscript's ps2 output is really a limited PDF output with a PDF 
> interpreter written in Postscript prepended. So it will be better or 
> worse depending. It's intended for printing, and doesn't currently 
> produce a DSC-conformant Postscript stream.

So ps2ps2 is not useful for producing eps files (say, to be embedded in 
a TeX document)?

> 
>> Does pdftops perform lossless conversion? Does ps2ps2? They both seem to 
>> produce better quality, but I'm not sure the conversion is completely 
>> lossless, by which I mean I can fearlessly convert between pdf and ps 
>> for ad infinitum and not worry about degradation in quality.
> 
> Completely lossless conversion between pdf and ps (or vice versa) isn't 
> possible. The best you can hope for is that they render identically, but 
> even that is difficult in some cases. It's best to pick one format for 
> your work and only convert to the other for printing or export.

Right, I am just hoping to render the results identically. (I'm not sure 
what other definitions of equivalence could exist, since the 
abstractions in both languages are incomparable, with postscript being a 
Turing complete programming language.)

The bottom line is that I'm getting different results from different 
tools, and I'd like to understand why.

> 
>> Why does pdf2ps yield abysmal results? My eye tells me it's rasterizing 
>> the fonts; is that true, and is that the only problem? Is there some way 
>> I can tell pdf2ps to produce high-quality output/can I use ghostscript 
>> to produce high-quality postscript-3? (I could find no documentation for 
>> pdf2ps on the website, and the man page is minimal.)
> 
> pdf2ps does rasterize a lot of fonts. Have you tried passing -r300 or 
> -r600 and seeing if that helps?

I can increase the resolution, but I was hoping for a solution that 
avoids rasterization altogether. And I'm not sure that's the only 
problem; I mention it because it's the most highly noticeable.

> 
>> Is postscript-2 inherently more verbose than postscript-3 (for 
>> equivalent constructs)?
> 
> If my postscript-3 you mean PDF, then yes, postscript level 2 is more 
> verbose for some documents. It offers fewer compression options, and the 
> image model is a subset, so some contents must be converted to less 
> abstract representation or rasterized.

By Postscript-3 I'm referring to the language standard. AFAICT this is 
not PDF....

> 
> Hope that's of some help.
> 
>  -r

Thanks,

Yang