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From Jeremias Maerki <...@jeremias-maerki.ch>
Subject Re: Line widths in PDF
Date Mon, 15 May 2006 12:23:34 GMT
If I understood Philippe correctly, he got that value from an OpenOffice
file. He said he'd try to change it. Anyway, despite this being a poor
use case, this is still something we should keep in sight. Even I have
seen strange effects of border painting inside Acrobat Reader because of
effects from anti-aliasing, for example, two border with the same width
but not displaying at the same width.

You're right. It's not a FOP bug, it's a glitch in Acrobat Reader but
always the easily reachable party is blamed. I have myself filed a bug
against Adobe Acrobat once before and never heard a word back. That's
life. :-)

On 15.05.2006 13:22:29 Chris Bowditch wrote:
> Jeremias Maerki wrote:
> > Philippe Drix made me look into why his borders don't show up properly
> > in Acrobat Reader and his printer.
> > 
> > He specified border widths as 0.002cm: 0.002cm = 0.0567pt = 0.02mm 
> :o I don't think this is a valid use case. Why would anyone want a 
> border so thin??? Just tell Philippe to widen his border to say 0.5pt. 
> Or provide a real world example of why such a thin border is required.
> > 
> > At 600dpi one dot/pixel is 1/600in = 0.00166666in = 0.12pt = 0.0423mm
> > 
> > So the border is less than half a pixel wide at 600dpi which is the
> > nominal resolution for most laser printers today. Even at 1200dpi you
> > don't have a full pixel, yet. 
> Yes I know. Precisely why I don't think anything less than 0.5pt is a 
> valid use case.
> > 
> > Digging into the source code, I found out: In FOP 0.20.5 horizontal and
> > vertical lines are painted as rectangles (0.056pt wide). In FOP 0.92beta
> > we're painting these lines as lines (0.056pt wide). So it appears that
> > Acrobat Reader handles the two differently. Apparently, it cannot be
> > said that FOP does something wrong per se. But the question pops up if
> > we should change the way we paint horizontal and vertical lines as part
> > of our border painting code.
> Actually I played a part in changing the border drawing code from 
> rectangles to lines. Using a rectangle to draw a line didn't seem 
> correct to me, when PDF provides a perfectly good line drawing command.
> > 
> > There's another thing. PDF allows to specify "0" as line width which
> > should result in 1 pixel on the target device. From the PDF Reference:
> > "However, some devices cannot reproduce 1-pixel lines, and on
> > high-resolution devices, they are nearly invisible. Since the results of
> > rendering such “zero-width” lines are device-dependent, their use is not
> > recommended." It would also be questionable how exactly we would
> > determine when to use "0" as line width. Probably not the best of ideas.
> > 
> > WDYT?
> I don't think FOP does anything wrong, so I'd leave it.
> Chris

Jeremias Maerki

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