Yes, the idea works, but the differences in hue are too small to be
useful in practice. And furthermore, they also show up for border lines
between adjoining polygons. I just want to highlight polygons that
completely overlap. I'm afraid I have to go the PostGIS/GEOS way.
Even o, would an XOR brush not be a nice addition to the STYLE object?
You could create all kinds of moiré fill patterns.
http://www.google.nl/search?q=moire&hl=en&client=firefox-a&hs=lGh&tbo=u&rls=org.mozilla:en-GB:official&tbm=isch&source=univ&sa=X&ei=C1UCUez4C9KX0QXV9IDoDw&ved=0CFMQsAQ&biw=1600&bih=809
Jan
On 1/24/2013 6:36 PM, Lime, Steve D (DNR) wrote:
You could try drawing the features with the same base color but with
opacity set. The more times the same area is rendered you'd get a
different hue.
Steve
*From:*[email protected]
[mailto:[email protected]] *On Behalf Of *Jan
Hartmann
*Sent:* Thursday, January 24, 2013 11:00 AM
*To:* Stephen Woodbridge
*Cc:* [email protected]
*Subject:* Re: [mapserver-users] Displaying overlapping linestrings
On 01/24/2013 05:35 PM, Stephen Woodbridge wrote:
On 1/24/2013 11:13 AM, Jan Hartmann wrote:
Does anyone know a trick to do this:
I'm making geographical indexes for the map series in our map
library.
Each map sheets is displayed as a polygonal linestring, based on its
corner coordinates. Lots of sheets have exactly the same
boundaries, so
it's not clear where a polygon indicates just one map sheet of
several.
It's easy, of course, to write a PostGIS query to return a different
color code when map boundaries exactly coincide, but I was wondering
whether something like that could be done by mapserver on its own,
like
XOR-ing a line with what is already there. Any ideas?
Hi Jan,
For polygons you could use a small negative buffer to shrink the
polygon slightly. You can do this in postgis, and you might be
able to do it with mapserver if geos is compiled in. See:
http://mapserver.org/development/rfc/ms-rfc-48.html
No, that is not what I meant. I'm looking for a trick for mapserver to
color a linestring differently when drawing over a linestring that it
has already drawn in a previous layer. In computer graphics you can do
this by using an XOR brush. Essentially, the screen frame buffer
functions as a sort of memory. I don not want to use PostGIS or GOS,
too complex. I doubt if this can be done by MapServer, but you never know.
Jan
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