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This is bugging me for years: When having large parentheses in LaTeX, the output file seems to contain little holes in the parentheses. It is not a big deal, but it's one of the areas, where LaTeX's output is not perfect. The problem is best seen in an example:

\documentclass{article}
\usepackage{amsmath}
\begin{document}
    \[\left(\frac{a}{b}\right)\]
    \[\left(\frac{\frac{\frac{a}{b}}{\frac{a}{b}}}{\frac{a}{b}}\right)\]
\end{document}

enter image description here Please note, that the small parenthesis looks perfect, whereas the large parenthesis contains some gray pixels, as can be seen in the zoomed version.enter image description here

Does anyone know where these error pixels come from? I have seen these errors in other peoples' formulas, too, so I think this bug is not only present on my system. Is it related to the viewer? I think I have seen the problem in printed documents, so this again seems to be unlikely.

Any idea how to locate and fix the problem?

Patrick Häcker
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    Do the white lines get thicker when you zoom-in using your pdf viewer (as opposed to when you resize the screenshot)? – John Wickerson May 20 '13 at 17:20
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    This is a viewer problem (and may be due to suboptimal hinting). – Hendrik Vogt May 20 '13 at 17:27
  • @JohnWickerson Interesting test, but no, they do not get larger. Depending on the viewer they might even get smaller when zooming-in (also depending on the exact zoom level). Although I guess that all my viewers user poppler, so this might not be an independent test set. – Patrick Häcker May 20 '13 at 17:28
  • @HendrikVogt Do you have any links to bug reports or any pointers to additional information? Is the hinting also applied when printing (much higher resolution)? This might be information for an answer … – Patrick Häcker May 20 '13 at 17:32
  • Possibly related: [link] – John Wickerson May 20 '13 at 17:33
  • @JohnWickerson, Thanks for the link. Unfortunately, I cannot reproduce that, as I do not have Adobe's reader and its installation failed just yet. So there are basically two possibilities: 1.) The reader does not do exact calculations. 2.) LaTeX does not do exact calcuations. – Patrick Häcker May 20 '13 at 17:53
  • @JohnWickerson, I tested xpdf's options -aa and -aaVector (antialiasing) and both do not solve the problem (in any combination). Of course, I do not know, if this is the same option as in Adobe's Reader in the given link. – Patrick Häcker May 20 '13 at 18:07
  • I just tested mupdf, and I cannot reproduce the problem in that viewer. So it might be related to the poppler library. Can anyone else see the described problem? – Patrick Häcker May 20 '13 at 18:31
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    It is likely a viewer problem. Questions of this sort pop up periodically on comp.text.tex. – jon May 20 '13 at 22:01
  • @JohnWickerson, ok, this is a viewer problem. As you have been the first to comment and added external ressources, would you mind posting an answer, so that I can accept it? – Patrick Häcker May 22 '13 at 08:48
  • I just filed a bug report: https://bugs.freedesktop.org/show_bug.cgi?id=64855 – Patrick Häcker May 22 '13 at 09:02
  • An aside: I think "tiny gaps" would be better than "tiny holes" in your title. "Hole" suggests something roughly circular, whereas "gaps" are long and thin. – John Wickerson May 22 '13 at 09:31
  • Thanks for the suggestion, I edited the title accordingly. – Patrick Häcker May 22 '13 at 10:09

1 Answers1

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If the gaps get thicker when you zoom-in using your pdf viewer, then they are "really there". If they stay just one pixel thick regardless of the zoom level, then, as Hendrik says, it's an issue with your pdf viewer.

[Here] is a possibly related internet link. In particular, it suggests

If you do see white lines in Acrobat, check the Page Display preferences, and make sure “smoothing” is turned on.

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John Wickerson
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