Comment 17 for bug 1476705
Revision history for this message
| cliddell (cjl) wrote Re: postscript printer hideously slow in some cases (pdftops) | #17 |
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73416ba
(Get the code!)
Bruno,
To be honest, I don't know what differs between the two tools, as they both come from Cairo, I assumed that pdftops was just a small wrapper around the same code as pdftocairo but with the options pre-set for PS output.
I'm a Ghostscript developer, so I can't really answer specifics about Cairo - I know about the problems with the Cairo PDF output, as we've performance problems in Ghostscript with those, and have had some fairly lengthy (and heated) discussions with Cairo developers on the subject.
And I have helped debug a lot of these problems with the Ghostscript output, so I can give general suggestions as I did above.
If I had to guess, I would say that pdftocairo is possibly spotting that the PDF originated as a Cairo file, and is using "inside" knowledge of how those are constructed to convert it back into Cairo internal representation, which is then outputs to Postscript - with that level of extra information, it can probably be much, much smarter about when there is real transparency that it has to render, and when everything opaque, and remain in high level form. Whilst, pstops may be doing a simpler, one step PDF to Postscript conversion.
Ideally, what you'd want to try is (if possible) to keep the "ProRes" (I thought it was "ImageRET") mode, but still tell pdftocairo to use 600 dpi, as you then may get the benefits of more the accurate dot placement, better halftone results, and possibly better color management, whilst keeping the quicker processing of the smaller image data.
It's hard to know without deep inside knowledge, but (again) if I had to guess, I would suggest that the slightly lower quality halftone screen is what's causing the slight intensity shift you mention. HP are pretty tight lipped about these technologies, but I know other such systems tend to allow the halftoning to represent more shades of the color, without losing detail (generally there is a trade off: you can approximate lots of shades, but lose detail, or have great detail, but very few shades).
Chris