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From Andreas Lehmkuehler <andr...@lehmi.de>
Subject Re: High res vs. vector
Date Sun, 10 Jan 2016 14:26:47 GMT

Am 09.01.2016 um 13:27 schrieb Tilman Hausherr:
> It really depends on what java printing and the printer driver do... our code is
> the same.
Hmmm, not really, see your comment bellow about creating an image first when 
choosing a dpi instead of using 0

> If I'd have a choice, I'd always use dpi=0 which will take the native printer
> resolution. This can be higher than 600dpi.
I agree, especially as we can't blow up the dpi of the given print graphics, 
e.g. the default dpi of CupsPDF printer driver on linux is 300 dpi

> Yes, using a specific dpi means that the print job will get bigger and bigger.
> Doing that means that an image is created first, and that one is rendered.
That are two possible issues with that approach (create an image first and print 
that to the printer graphics device as a whole)

First of all the printer graphics may by at a lower resolution as the image 
itself (300dpi vs. 600 dpi), so that some may be some quality loss when 
downsizing the image to the lower resolution.
More important is a possible second effect. If dpi = 0 is used all painting is 
done directly to the printer graphics device which produces a vectorized pdf (at 
least in my case using the CupsPDF printer driver and I guess it's the same with 
the XPS driver). Such a vectorized pdf can be scaled easily to any resolution. 
If dpi > 0 is used an intermediate image with the given dpi is created and 
printed as whole to the printer graphics device which produces a pdf consisting 
of one single image which can't be scaled without quality loss.

Saying that, to choose another dpi resolution than the default IMHO makes sense 
only if rendering to an image for further usage other than printing.

> I tried printing from PDFDebugger which uses default settings (dpi = 0) and can
> confirm that the color parts look blurry in XPS. (Btw these are NOT images, the
> only image is the printer symbol) However I did it with CIB PDF brewer (i.e. I
> printed to a PDF file) and it looks fine. I also tried to print the XPS file
> with CIB but then I got a null pointer error, so I can't test that one (this is
> a bug in XPS or in CIB). I wanted to do that to find out whether the contents of
> the XPS file are bad, or just the display. Please try this yourself. A software
> similar to CIB is e.g. PDF Creator.
And maybe the XPS driver is a third reason for an issue in the given use case.

> Tilman
> Am 08.01.2016 um 16:46 schrieb Tres Finocchiaro:
>> Correction....
>> To be able to represent this visually, I've taken the following picture of
>> a rendering done using each approach and sent to the XPS Document writer:
>> ** *http://i.imgur.com/nBaaJoP.png *(i had incorrectly marked each
>> rendering)*
>> - Tres.Finocchiaro@gmail.com
>> On Fri, Jan 8, 2016 at 10:44 AM, Tres Finocchiaro <
>> tres.finocchiaro@gmail.com> wrote:
>>> Hi,
>>> I'm trying to determine the best way to achieve high resolution PDF
>>> printing with PDFBOX 2.0.
>>> Our programmer recently wrote some logic to use PDFPrintable but I noticed
>>> the fonts were rasterized, so I started converting the code to use
>>> PDFPageable instead (since we had upgraded from a system which used
>>> silentPrint()).  However, I'm having mixed results.
>>> What I've found is:
>>>     - When DPI (such as 600dpi) is provided as a parameter to PDFPageable,
>>>     the images render much nicer, but the fonts get rasterized.
>>>        - Rasterizing the fonts seems to make the print job much, much
>>>        larger.
>>>        - Rasterizing the fonts is observable at a high zoom factor (not
>>>        observable to the naked eye).
>>>     - When the default DPI is provided (AFAIK, Zero, or simply omitted),
>>>     the images render quite grainy, but the fonts appear vector.
>>> To be able to represent this visually, I've taken the following picture of
>>> a rendering done using each approach and sent to the XPS Document writer:
>>> http://i.imgur.com/JlTpGht.png
>>> The PDF we're using is available for preview and download here:
>>> https://github.com/qzind/qz-print/blob/2.0/assets/pdf_sample.pdf
>>> So the question is, why does a higher DPI have a negative effect on
>>> rendering?  Are we not using this improperly?  Thanks in advance!
>>> -Tres
>>> - Tres.Finocchiaro@gmail.com


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