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[GEMPAK #IVW-188177]: GIF Palettes

> I've been using GPMAP to create a base map and then displaying NIDS data
> on top of that with the GIF driver.  Things are working great but I've
> noticed that there is no consistency in regards to where it places
> colors (what index #) on the color palette.  One image may have yellow
> (255,255,20 for instance) in index #3 and then in the next image from
> the same site it is in index #5.  I'm currently using the LUTSFIL
> variable to apply a specific color palette for GEMPAK to use.  Is there
> any way to get it to use a consistent palette inside the file?
> 
> Thanks
> Kelly Koehn
> 
> 
> 


Kelly,

The GIF device color indicies are generally entered into the table in the order 
that they
are used in the image (note that if you don't use a color, it won't be in the 
index). 

On the other hand when you use the GF device, the color index table
of the output file is created from the color lookup table, which should be 
consistent, though you
cannot later change the vaolues of color indicies in the color table as you 
would be able 
to with the GIF driver through the GPCOLOR program.

As a result, you could use the GIF driver with MAP=5, and then later use 
GPCOLOR to
redefine color 5 to be something else, eg COLORS=5=R:G:B and further plot
with more colors than were in the original coltbl.xwp and lutfil. This
would not work with the GF driver.

If you are trying to change the color values in an external graphic package, 
the best way would be 
through the RGB values and not rely on index entries in the output file.

Steve Chiswell
Unidata User SUpport

Ticket Details
===================
Ticket ID: IVW-188177
Department: Support GEMPAK
Priority: Normal
Status: Closed