[Bug 688243] Spurious lines between joined filled rectangles and antialiasing (fwd)

[Petr M. <mi...@ph...>]

Below is a answer to the bug report by ghostscript people. The referenced 
bug 687742 refers to ghostscript documentation, where, amazingly, you can 
read the following:

-dTextAlphaBits=n
-dGraphicsAlphaBits=n
     These options control the use of subsample antialiasing. Their use is 
highly recommended for producing high quality rasterizations. The 
subsampling box size n should be 4 for optimum output, but smaller values 
can be used for faster rendering. Antialiasing is enabled separately for 
text and graphics content. Allowed values are 1, 2 or 4.

     Note that because of the way antialiasing blends the edges of shapes 
into the background when they are drawn some files that rely on joining 
separate filled polygons together to cover an area may not render as 
expected with GraphicsAlphaBits at 2 or 4. If you encounter strange lines 
within solid areas, try rendering that file again with 
-dGraphicsAlphaBits=1.

I'm asking about how to switch GraphicsAlphaBits from within the ps code...


---------- Forwarded message ----------
Date: Wed, 27 Jul 2005 13:10:25 -0700 (PDT)
From: bug...@gh...
Subject: [Bug 688243] Spurious lines between joined filled rectangles and
     antialiasing

http://bugs.ghostscript.com/show_bug.cgi?id=688243

------- Additional Comments From ale...@co...  2005-07-27 13:10 -------
Created an attachment (id=1578)
  --> (http://bugs.ghostscript.com/attachment.cgi?id=1578&action=view)
foo.ps -- modified sample

This is an old and rather difficult to fix issue. See the bug 687742 for the
discussion. gnuplot can try to write adjacent boxes in the single fill
operation but this is not possible when the bxes have different colors.
See the modified sample file.