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-boun...@lists.osgeo.org [mailto:mapserver-users-boun...@lists.osgeo.org] On Behalf Of Jan Hartmann Sent: Thursday, January 24, 2013 11:00 AM To: Stephen Woodbridge Cc: mapserver-users@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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