garp/gempak modifications for 16- and 24-bit graphics

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Hi...                                         July 23, 2002

I bit the bullet and decided to try my hand at modifying the
garp/gempak package for 16- and 24-bit graphics modes.  I seem
to have achieved success in doing this and wonder if my changes
can be included in a future release of gempak to both benefit
the community and also eliminate my need to update the package
every time a new release is made.

The philosophy of the update was to minimize changes to the
overall code while adding the capability to support 16- and 24-bit
modes.  The functioning of the original 8-bit mode is retained
almost completely for backward compatibility purposes.  The changes
were accomplished by maintaining the existing 8-bit images
internally and using data mapping to convert the images to 16-
or 24-bit when the images are displayed on the screen.  This takes
more graphics memory but seems to work fine in 16-bit mode on
modern PC's.  24-bit mode gets a bit pokey.  Color tables are
handled by converting screen imagery values to the appropriate
read-only color cells rather than modifying the pseudo-color tables.
This necesitated reloading of imagery upon changing lookup tables
since the images are modified and reloaded to reflect changes in
the lookup table rather than modifying the actual (read-only) table
itself.  Endian issues are addressed so the modified package is
supported on big- and little-endian machines.

The actual number of code modifications proved to be fairly minor
although the time in finding the right spots was fairly major :)
I've done quite a bit of testing and intend to run the package
operationally at the beginning of our Fall semester on V7.3 of
RedHat.  However, I would consider the code beta quality since
I have not tested it exhaustively.  All the modifications were
made to code from the V5.6.f release of gempak.  I'm attaching
a tar file with the new sources (modified ones only) for your
perusal.  The tar file is designed to extract into $NAWIPS and
overwrite the existing sources, so be careful where you unpack it.

Please let me know whether you think these changes can be
incorporated into a future release.  If you find any problems that
need further work, let me know and I'll try and do what I can
to fix them.

                             Thanks.

                               Art.

Arthur A. Person
Research Assistant, System Administrator
Penn State Department of Meteorology
email:  address@hidden, phone:  814-863-1563