Bug 692120

Summary:	Text antialiasing breaks at large point sizes
Product:	Ghostscript	Reporter:	Marcos H. Woehrmann <marcos.woehrmann>
Component:	Text	Assignee:	Chris Liddell (chrisl) <chris.liddell>
Status:	NOTIFIED FIXED
Severity:	normal	CC:	chris.liddell
Priority:	P2
Version:	master
Hardware:	PC
OS:	All
Customer:	200	Word Size:	---

Description Marcos H. Woehrmann 2011-04-04 18:08:23 UTC

The customer reports:

We have been using the ghostscript jpeg device to generate JPEG’s from postscript. In the transition from version 8.64 to 9.0 the quality of large text sizes have diminished – as the anti-aliasing automatically turns off at some pixel size of the characters.
 
The attached postscript file illustrates the problem.
 
The attached jpeg’s were generated by ghostscript using the options:
-dSAFER -dBATCH -dNOPAUSE -dEPSCrop -sDEVICE=jpeg -dJPEGQ=100 -dGraphicsAlphaBits=4 -dTextAlphaBits=4 -r132.0

Comment 2 Marcos H. Woehrmann 2011-04-04 18:10:10 UTC

Ken took a look at this and reports:

With -dDisableFAPI=true the text is always anti-aliased regardless of point size. With FAPI enabled the text is anti-aliased up to a point (~84.6975), presumably where the glyphs grow so large we stop caching them, and from then on is not anti-aliased.

I'm not sure why not caching should cause the problem, but it does seem to be FAPI related.

While we will want to fix the problem, you could suggest using -dDisableFAPI=true as a temporary work-around.

Comment 3 Chris Liddell (chrisl) 2011-04-05 15:04:14 UTC

fixed in r12369.


The patch can be seen here (it is fairly simple):
http://www.ghostscript.com/pipermail/gs-cvs/2011-April/012645.html