[GRASS5] Fw: d.area progress report...

[Eric G. Miller]

On Sat, 26 Jan 2002 06:41:23 +0100, Radim Blazek <radim.blazek at wo.cz> wrote:

[snip]
> Very simply, from last point of area to first of isle and from last of isle 
> back to last of area. But I have tested only with simple data and some
> problems may occure later. But in that case I would prefer improvement of
> G_plot_polygon. You can see the code in d.vect / g51. (And test in grass51)

Yea.  I think you got lucky.  Try it with non-convex polygons with little
holes spread around in nooks and crannies.  Also, don't draw unlabeled
areas, they'll mask the outcome.

I'm thinking G_plot_polygon, or a derivative, could be modified and either
present a three part interface as previously described or a single function
that can take **xs, **ys, and *n for inputs.  It would have to process the
edges of each ring (finding the scanline intersections), before moving on
to do the point sort and generating the fill start/stop extents.

What I don't understand is why any of these functions are in libgis.  IMHO,
they should all be in the display library (and the display and raster libes
should be merged).  One problem encountered is there's more than one method
used for world/screen coordinate mappings, and they aren't consistent.

Anyway, I'll play around with it a little...

-- 
Eric G. Miller <egm2 at jps.net>