[gradsusr] lines in eps output

[Frank Colby]

Oscar,

This is an email I found in my email archive, that might help you with 
your lines.

Frank

**********


On Fri, Jul 17, 2009 at 3:17 AM, Dhaval Prajapati 
<dhaval.prajapati at iccsir.org <mailto:dhaval.prajapati at iccsir.org>> wrote:

     Hi,

    I have prepared  . ps files using grads. Now in the file there are
    horizontal lines coming for colors
    How to remove it?
    is there any command to get batter images?
    I am attaching one file for sample in both .ps and .jpg format



Try "gxyat" that comes with the opengrads bundle (available from 
http://opengrads.org). Basically, gxyat is a replacement for "printim", 
although it can produce .ps, .pdf and .svg output. More info here:

     http://opengrads.org/wiki/index.php?title=Gxyat

Some remarks on these "lines":

1) The "lines" you are referring do not appear if you print your 
postscript file on paper, only on the screen.  These "lines" come from 
an artifact of the grads shading algorithm and the anti-aliasing 
algorithm used by the programs that display postscript on the screen. 
 However, depending on your display program, sometimes you can turn 
anti-aliasing off and the lines go way. However, the fonts do not look 
as good.

2) When you convert your postscript to jpg, anti-aliasing is usually 
applied and you get the "lines". Again, depending on your conversion 
program you can turn anti-aliasing off and get rid of the "lines" at the 
expense of jagged fonts.

3) What "gxyat" does when creating image files (.png in this case) is to 
use anti-aliasing when drawing lines and turn anti-aliasing off when 
doing polygon fills. In the end you get smooth fonts and no "lines". In 
addition, "gxyat" gives you a lot more flexibility with transparency.

4) If you write .ps/.pdf files with gxyat you will have the same problem 
with the "lines". The reason is that there is no way (that I know of) in 
postscript to turn anti-aliasing on/off for part of a page, it is all or 
nothing.

BTW, you can use "gxyat" from the grads command line (replacement for 
"printim"):

ga-> gxyat image.png

or from the OS command line (replacement for gxpng, gxeps):

$ gxyat -o image.png image.gmf

where "image.gmf" is a grads metafile.  The SVG output is very useful to 
import grads output into vector graphics programs such as Adobe 
Illustrator or Inkscape without loosing any resolution (great for posters).

It would be great if someone could contribute a recipe to the Cookbooks 
illustrating these points.

   Arlindo


-- 
Arlindo da Silva
dasilva at alum.mit.edu <mailto:dasilva at alum.mit.edu>
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