This problem is not solvable, at least not completely:
1. You draw a stave with graphical operators
2. You draw stave notes as glyphs of a font.
3. You render it to an image with in this case much too low resolution
(141.146 dpi)
So we have here either splash or cairo (for drawing the stave) and
freetype (for drawing the glyphs) which draw it to an image without
having pixel boundaries.
This problem was discussed a lot of times also in the bug reports, s.
i.e. https://bugs.freedesktop.org/show_bug.cgi?id=37347
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)
Cheers,
Thomas
Am 26.03.2017 um 22:11 schrieb William Bader:
When I open the test PDF in atril (the Mate desktop version of evince)
and change the window size (with 'fit page width'), once I get below
about 80%, small changes make the bars of the staff go up and down,
and not all of the bars of the staff shift equally, so the space
between the bars is not equal, and that might contribute to the effect
that the notes are misplaced. I am not sure, but it seems as if it is
not antialiasing the bars. When you reduce the image to the point
where pixels are significant and the total number of pixels is not the
exact amount to leave the same number of pixels between each bar,
rounding can't create more pixels. You need to simulate fractional
pixels through antialiasing. The 'w' command in PDF sets the line
width. It looks like it is drawing lines of 0.4, 0.65, 0.8, and 1
point. The tests for thinLineMode are in splash/Splash.cc.
William
------------------------------------------------------------------------
*From:* poppler <[email protected]> on behalf of
[email protected] <[email protected]>
*Sent:* Sunday, March 26, 2017 12:34 PM
*To:* Albert Astals Cid; [email protected]
*Subject:* Re: [poppler] Scaling factor and placement accuracy
>> ourParent->document->setRenderHint(Poppler::Document::Antialiasing);
>> ourParent->document->setRenderHint(Poppler::Document::TextAntialiasing
>>ourParent->document->setRenderHint(Poppler::Document::ThinLineSolid);
>Tried thin line shape instead of thing line solid?
Thanks, Albert, I just tried it, same result.
I spent a couple hours last night trying to find the area of code that
does the actual placement without any real luck, to see if there is
any kind of rounding issue. I saw a lot of other possible areas like
anti-aliasing, but basically got lost in the code because I don't know
enough to know what is actually inside the PDF (I tried
PDFStreamDumper and can see what's inside, and even seeing it I do not
understand it).
So far making the x/y scale factor integral appears to avoid the
problem; it's hard to prove a negative, but I have not seen it occur
in that case. This just very slightly throws off the desired size I
want, and I just needed to put a proper color border into the overall
page to avoid showing an outline, so it's very workable for what I
want, if it keeps working.
Thanks again,
Linwood
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