[gs-bugs] [Bug 691455] Stroking of sloppily authored paths goes wrong.

bugzilla-daemon at ghostscript.com bugzilla-daemon at ghostscript.com
Wed Jul 14 07:19:38 UTC 2010


http://bugs.ghostscript.com/show_bug.cgi?id=691455

Ken Sharp <ken.sharp at artifex.com> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|REOPENED                    |RESOLVED
         Resolution|                            |INVALID

--- Comment #15 from Ken Sharp <ken.sharp at artifex.com> 2010-07-14 07:19:36 UTC ---
(In reply to comment #13)
> Created an attachment (id=6477)
 --> (http://bugs.ghostscript.com/attachment.cgi?id=6477) [details]
> correct-render.png
> 
> Added an attachment showing how the other render engines would render the
> previous postscript test. These renderings all have a final cap that is
> perpendicular to the line between the two last coordinates of the final
> curveto.

Which other engines? 

I used Jaws (a different PostScript rip) to render the test file and it agrees
with Ghostscript. I also used Adobe Acrobat Distiller to convert to a PDF file
and examined that in Acrobat. While the first two lines do match the .PNG file,
the third line does not, the three leftmost and the rightmost verticals are
shown with butt end caps.

According to Robin's comment #10 Acrobat does not draw the same path when using
strokepath, and is therefore unreliable as it should do so. It also doesn't
match the 'reference'.

Comparisons with SVG and SVG rendering engines are irrelevant, we are consuming
PostScript. It is entirely possible that the PostScript generation is incorrect
and does not match the correct result in SVG, that would be a bug in the
PostScript generation.

It would be interesting to see the result from an Adobe CPSI rip, and also from
a Harlequin rip to give a couple more data points. It would be important to
also check the strokepath result to ensure the implementation is reliable
(unlike Acrobat).

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