How to remove horizontal lines in Output

[Arlindo da Silva]

On Fri, Jul 17, 2009 at 3:17 AM, Dhaval Prajapati <
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
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