[GRASS5] [bug #242] (grass) R_polygon_abs() seems to ignore islands

[Glynn Clements]

Eric G. Miller wrote:

> > If d.area converts to rasters, the HTMLMAP driver isn't likely to be
> > much use.
> 
> True, but I wouldn't run d.area for HTMLMAP anyway, since the main point
> of d.area is doing filled polygons (though d.vect doesn't currently
> handle the hole scenario at all).

HTMLMAP/README says:

  The only GRASS display commands that should be used with this driver are:
	d.text	 - pass href information for resulting image maps.
	d.area	 - draw polygons from a vector file.

> I think HTMLMAP could be better done as a module rather than a
> display target anyway.

Quite possibly, given that it's significantly more restricted than all
of the other "display" drivers. Although there may be some advantage
in being able to use command sequences similar to those used for
generating the image (e.g. with PNGDRIVER).

> > More generally, rasterisation reduces the information content. 
> > Presumably there are other vector operations which should be able to
> > handle shapes which aren't convex polygons.
> 
> Much of this problem is specific to drawing routines for fill.  There
> are some elements that would be applicable for union/intersect type
> operations (though we need real attribute support before such things
> will have much utility).  When I was referring to rasterization, I was
> specifically thinking of display.  For hardcopy (map files) keeping
> vector is better...

Yep; and it's not an issue for ps.map; PostScript handles shapes with
holes fine. If I were looking to rasterise complex shapes, I'd
probably look at ripping the code from Ghostscript.

-- 
Glynn Clements <glynn.clements at virgin.net>

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