[GRASSLIST:5814] Re: PNG hardcopy scripts revisited

[Eric G. Miller]

On Fri, Mar 21, 2003 at 12:22:53AM +1200, H Bowman wrote:

> In producing these, I've noticed that I get slightly different output
> depending on which one I use. Particularly the PNG driver seems to be
> suffering a similar, yet different, bug as the d.area vs d.vect
> off-by-one translation bug.  Zooming way in on the PNGs shows that the
> vector layer is the same pixel by pixel in both, but the rasters are
> slightly different (not just datum off-by-one as far as I can tell and
> the following image suggests), but 'grown'. Not a big worry, but it
> degrades the quality of the PNG-driver output.

It's a bug in d.area -- well, not really d.area, but in the coordinate
transformation routines it calls.  d.vect.area and d.vect.line do not
suffer from that problem (well, they are consistent with d.vect, whether
one considers the method of translation correct or not).

When I wrote d.vect.area, I intended to remove d.area, since it has
other significant problems as well.  But d.vect.area doesn't work well
with the HTML driver because the data is rasterized before it is sent
to the display driver (since the display protocol has no way to
correctly draw polygons with holes).

-- 
echo ">gra.fcw at 2ztr< eryyvZ .T pveR" | rot13 | reverse