[Lilypond-auto] Issue 2658 in lilypond: wrong stem rendering (inconsistent thickness)

[lilypond]

Status: Accepted
Owner: ----
Labels: Type-Defect

New issue 2658 by address@hidden: wrong stem rendering (inconsistent  
thickness)
http://code.google.com/p/lilypond/issues/detail?id=2658

SUMMARY: see animation.gif [1] (make sure it displays sharp [2] - it  
shouldn't be viewed zoomed)

Stems in LilyPond aren't just lines - they are rounded rectangles.   
Unfortunately rounded rectangles are often displayed badly in pdfs (their  
thickness isn't consistent), and it seems that the same problem is present  
on printouts [3].
Depending on application used for viewing the output, this effect may be  
more or less visible: some applications use rounding to display straight  
vertical/horoziontal lines sharply, some don't do rounding and use shades  
of grey [4].  The inconsistent stem thickness is very noticeable in apps  
which use rounding (e.g. Acrobat Reader and Frescobaldi).

As you can see in the animation [1] and images [5], stems don't have  
consistent thickness across one rendering AND they are displayed  
differently at different resolutions/zooms.  This clearly indicates that  
the problem is related to wrong rounding of stem edges' positions.

I've found out that simple postscript lines don't have such problems  
(that's why staff lines are fine - they are lines, not rounded  
rectangles).  It can be seen in the images: the top line is default Lily  
output, middle line has stems displayed using simple lines, and bottom line  
uses rounded rectangles to confirm that they cause the trouble.

It would be best to make rounded rectangles display correctly (maybe we  
didn't use some switch in PostScript?), but if that turns out to be  
impossible, what about displaying stems as simple lines?

Oh, and this doesn't concern only stems: every object displayed as rounded  
rectangle has this problem (e.g. LyricHyphens).

[1] top and bottom: current Lily, middle: desired
[2] displays correctly in Firefox (Win7 & LilyDev), wrongly in IE
[3] to a lesser degree, of course, as printers have higher resolution than  
monitors.  I've examined a printout from 1200 dpi laser printer and there  
were slight - but still visible - inconsistencies in thickness.
[4]  
http://lilypond-stuff.1065243.n5.nabble.com/file/n5705601/rounded-vs-not-rounded-display.png
[5]  
http://lilypond-stuff.1065243.n5.nabble.com/file/n5705601/%7E100_dpi.tar.gz
     
http://lilypond-stuff.1065243.n5.nabble.com/file/n5705601/%7E200_dpi.tar.gz
     
http://lilypond-stuff.1065243.n5.nabble.com/wrong-stem-rendering-inconsistent-thickness-td5705601.html

Attachments:
        animation.gif  18.2 KB