[mapserver-users] Displaying overlapping linestrings
Jan Hartmann
j.l.h.hartmann at uva.nl
Fri Jan 25 01:49:52 PST 2013
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:*mapserver-users-bounces at lists.osgeo.org
> [mailto:mapserver-users-bounces at lists.osgeo.org] *On Behalf Of *Jan
> Hartmann
> *Sent:* Thursday, January 24, 2013 11:00 AM
> *To:* Stephen Woodbridge
> *Cc:* mapserver-users at lists.osgeo.org
> *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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