new software Gtk2::GIS

[Ari Jolma <ari jolma tkk fi>]

I've just uploaded to sourceforge a set of new versions of my libral,
Geo::Raster and of Gtk2::GIS which is a new Perl module. Gtk2::GIS is a
simple, but hopefully powerful, GIS which builds on Perl/Gtk2, a new
Gtk2 widget for displaying rasters (subclassed from ScrollableWindow),
Geo::Raster, Geo::Shapefile, and libral. This release contains a lot of
self-test code in Geo::Raster, and code cleanup in libral but it should
still be treated as an experimental package. The Gtk2::GIS is an initial
release and contains just the basic functionality. I call Gtk2::GIS a
GIS but it actually is just a set of interoperating Gtk2 widgets which
can be used as such in an application but can also be extended/embedded
in custom applications.

The packages are at http://sourceforge.net/projects/libral/

I've submitted a proposal to OSG'05 to present this software in a 90
minute session but briefly said it is a low level raster algebra library
with a Perl interface and now Perl/Gtk2 GUI. I was in fact surprised to
see how appealing and useful the graphical interface could be since the
libral and Geo-Raster require that overlayed rasters are of same size
and have the same world coordinates. In the GUI, however, since it works
on only world coordinates, it is possible to visualize all kinds of
rasters (and vector data) at the same time. Then, with zooming and
panning the user can go to the place of interest, clip out overalyable
rasters from the visible area and work on those and put the result to
the GUI. Because the GUI is in Perl, it was easy to add an interactive
shell which can be used side by side with the GUI. Also exteding the GIS
is easy as long as one is happy with Perl. Such shell was included in
Geo-Raster previously but the graphics was done with PGPLOT with only
one raster at a time.

I also added support for Shapefiles into Gtk2::GIS using my
Geo::Shapefile (which is a Perl interface to Frank Warmerdam's
shapelib). It works ok but shapefile and raster layers really need to be
made equivalent, i.e., support transparency and layering (now shapefiles
are rendered after rasters). By the way, does anybody know of good
algorithm for rendering (including transparency) polygons as they are in
Shapefiles (non-complex but having potentially holes)?

And, sorry, all this is distributed only as source code and, while
cross-platform in theory (C, Perl and Gtk2 are all cross-platform), is
maybe not simple to build on a non-GNU environment.

Ari Jolma