[poppler] Scaling factor and placement accuracy

[Thomas Freitag]

Am 27.03.2017 um 16:06 schrieb pqt at LEFerguson.com:
>
> Thomas, thanks.
>
> >If anyone is able to develop a pixel scissors I would take a deeper 
> look into it
>
> >(and would nominate him to get a Nobel Prize J ), in the meantime I would
>
> >advice to take a much higher resolution when render it to an image (at 
> least 300 dpi)
>
> I'll put that on my list.  As soon as I finish up Maxwell's Demon 
> (virtual of course) I think I can put him to work splitting pixels as 
> well sorting molecules.
>
> But maybe you can advise as to resolution.  I am displaying on a 
> 1920x1080 monitor.  The goal is to receive back from poppler a QImage 
> that doesn't have to be resized to display in a QLabel.  I'm 
> calculating the 141+ based on the definition of the field to yield a 
> specific pixel dimension of the result (and it does); I didn't even 
> realize this was intended as dpi until I saw the units in the code (I 
> just inverted the math based on the definition of 72's, etc.)  The dot 
> pitch on that monitor is about 102 dpi, but the PDF is … well, who 
> knows how Musescore specified it.
>
> Am I thinking of this incorrectly -- won't I get the best quality (and 
> best performance) letting Poppler render exactly the pixel dimensions 
> I will display on the screen?
>
I fear that You never will get a result which is completely satisfying 
in this case. I attach a very old memo once again here which tries to 
explain the problem.
But probably you can get a better result when you render it in a high 
resolution (i.e. 600 dpi) and then resize it for displaying. I played a 
little bit around with it, the  stave lines will get different shapes 
then, but at least they are centered to the stave notes.

Cheers,
Thomas
>
> Thanks again,
>
> Linwood
>

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