[gs-bugs] [Bug 692132] displayed Fonts in final pdf are not correct

[bugzilla-daemon at ghostscript.com]

http://bugs.ghostscript.com/show_bug.cgi?id=692132

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

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

--- Comment #1 from Ken Sharp <ken.sharp at artifex.com> 2011-04-07 12:54:30 UTC ---
The original PostScript file consists of a Quark Express output, which draws
all the text uaing a Quark type 3 font to achieve special text effects. In this
case it looks like artificial emboldening.

This is done by drawing the text twice. First the text is drawn using 'show',
then it is converted to a path using 'charpath' and the resulting path is
stroked. Note that there is no direct equivalent to 'charpath' in PDF, so some
action needs to be taken to represent this.

Ghostscript preserves this by emitting type 3 fonts which mimic this action. We
first 'show' the text from the original font, then stroke a path which is
created (and stored) from the original font when the PDF was created.

Distiller decomposes the type 3 font, and performs each operation separately.
So it first draws the text, then restores the position, and draws the text
again.

Provided that the path used to 'show' the text in the PDF file, and the path
created at the time the PDF is created are the same, the result is equivalent.
It seems, however, that Acrobat is treating these two differently. As a result
they do not line up perfectly. If you zoom in to the Acrobat display you will
see that these discrepancies progressively disappear. That is, as the effective
resolution increases, the difference between the stored path and the path
created from interpreting the font decreases.

I believe this is an artefact of the way that Acrobat attempts to produce a
more 'pleasing' result from text, particularly at low resolution. Rendering the
two PDF files with Ghostscript does not show the same effect, nor does MuPDF.

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