[OS X TeX] Line thickness in TeXShop preview (and Preview.app) on Tiger

William F. Adams wadams at atlis.com
Sat May 14 15:11:17 CEST 2005

On May 12, 2005, at 5:18 AM, Bruno Voisin wrote:

> It seems that in TeXShop's preview window on Tiger (hence with version 
> 2.02) the thickness of lines, as produced by underlining or in tables, 
> varies: some lines have (what looks like) one pixel thickness, while 
> others have two pixels thickness.
> This appears to be connected with the magnification: at 100% or 200% 
> all lines have the same thickness, but when the PDF document isn't 
> displayed at an integer multiple of its original resolution, for 
> example with 150% magnification, the thickness starts to vary. Local 
> rounding artifacts when mapping from the document resolution to the 
> screen resolution, when the two are no integer multiples of each 
> other?
> Preview.app exhibits the same behaviour, thus it seems to be connected 
> with Apple's routines used by TeXShop. I was accustomed to this 
> behaviour in OzTeX, but don't remember seeing it in TeXShop before 
> Tiger.
> Screenshots here <http://homepage.mac.com/bvoisin/FileSharing4.html>. 
> (Sorry for the "-zip.zip" extensions, I've no idea of how it got there 
> and tried everything I could think of to get rid of it, with no luck.)

This is a function of how TeX draws lines. Instead of using a 
PostScript ``moveto'' and ``stroke'' operator, it defines a rectangular 
region and fills it.

This means that it's subject to rounding errors as you noted, but this 
can be ameliorated by anti-aliasing and other rendering settings.

In the past, I recall such dropping out completely quite often at lower 
magnifications, so it seems that Apple has set things so that they 
always render, resulting in the results you see.

Frank Mittelbach spent a fair bit of time checking his macros for _The 
LaTeX Companion 2nd Ed._ because of the publisher being concerned with 
this in the proofs.


William Adams, publishing specialist
voice - 717-731-6707 | Fax - 717-731-6708

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