[OpenLayers-Users] WMS polygon fill color

[IvanBell]

What is the best strategy for coloring a polygon in a map?  I am using WMS
and my map contains polygon layer(s) in which I wish to change the colors
based upon some dynamic information.


The map is a floor plan consisting of several layers (a campus, building,
section, room, and detail polygon layer on top of a vectored image drawing
of the campus/building).  I have found that by creating a Polygon feature in
a vector overlay, I can achieve my goal.  However, I ran into a problem with
using Internet Explorer 8.  It seems that IE does not support SVG, only VML,
and that VML starts to creep when adding too many features to a map.  "Too
many" [for me] appears to be 40.  Firefox and Chrome load the map
instantaneously; but IE takes 45 seconds for just 40 polygon features.  This
number is but a fraction of what I need to add; so, I really need help to
solve this.





            coloredPolygonLayer = new OpenLayers.Layer.WMS(
               "Colored Polygon Layer",
               {
                  displayInLayerSwitcher: false,
                  isBaseLayer: false
               }
            );

            var red = {
                strokeColor: "#800000",
                strokeOpacity: 1,
                strokeWidth: 2,
                fillColor: "#FF0000",
                fillOpacity: 0.7
            };
            var blue = {
                strokeColor: "#000080",
                strokeOpacity: 1,
                strokeWidth: 2,
                fillColor: "#0000FF",
                fillOpacity: 0.7
            };

            //
            // Fill the red polygons.
            //
            var polygonGeometries = [];
            polygonGeometries.push( "660.9979763,-450.06682014
663.68078041,-446.75461388 683.77661324,-447.03618622
683.85334587,-485.23556328 682.4714489,-493.15101433
675.89935875,-494.919487 664.72382164,-485 661.58379173,-484.58379173
660.93322945,-452.20343971 660.9979763,-450.06682014" );
            polygonGeometries.push( "703.94480705,-446.4528904
703.97554207,-448.92936516 703.62247276,-484.80152512
700.20403099,-486.69899178 699.01870537,-494.97194099
691.6276722,-491.50213814 682.07145119,-481.42777443
681.64668465,-447.09778786 703.94480705,-446.4528904" );
            ...
            fillPolygons( coloredPolygonLayer, polygonGeometries, red );


            //
            // Fill the blue polygons.
            //
            polygonGeometries = [];
            polygonGeometries.push( "724.09494972,-372 726.3353672,-372
741.87992287,-371.93996048 744.00000191,-394.06738853 736.00000191,-406
725.00000191,-419 722.08182335,-414.23610878 724.09494972,-372" );
            polygonGeometries.push( "745.35787392,-371.64212608
767.78647041,-371.10543823 765.72203255,-409.48135376
757.43100548,-417.14139557 748.8010273,-417.10012817
745.41958427,-411.84170532 752.00000191,-406.38969803
742.34921837,-396.52966118 744.00000191,-373.90360832
745.35787392,-371.64212608" );
            ...
            fillPolygons( coloredPolygonLayer, polygonGeometries, blue );



            ...



         function fillPolygons( layer, polygonGeometries, style ) {
            //
            // Parse geometries to get the specified polygons. 
Specifically,
            // parse the points of the polygon and add them to the linear
ring
            // array.  The linear ring defines the boundary of each polygon.
            //
            // This parsing is only necessary since store the polygon
geometries
            // in the same format as sent from the map server (i.e., a
            // space-delimited string of point sets, each set being
            // comma-delimited.
            //
            var linearRings = [];
            var polygonPoints = null;
            var polygonPoints = null;
            var nextPoint = null;

            for ( var i = 0; i < polygonGeometries.length; i++ ) {
               polygonPoints = polygonGeometries[ i ].split( ' ' );

               polygonPoints = [];
               nextPoint = null;

               for ( var j = 0; j < polygonPoints.length; j++ ) {
                  nextPoint = polygonPoints[ j ].split( ',' );
                  polygonPoints.push( new OpenLayers.Geometry.Point(
nextPoint[ 0 ], nextPoint[ 1 ] ) );
               }

               linearRings.push( new OpenLayers.Geometry.LinearRing(
polygonPoints ) );
            }

            //
            // Fill selected polygons.
            //
            for ( var i = 0; i < linearRings.length; i++ ) {
               layer.addFeatures( [ new OpenLayers.Feature.Vector(
linearRings[ i ], null, style ) ] );
            }
         }




I am a newbie to OpenLayers and, for the most part, I have been able to
solve most every problem that I have (e.g., highlight polygon, select
polygon, drag marker, styles, etc.).  This one has me stumped.


The polygons that I am coloring have significance only at the time the map
is loaded.  I.e., their color represents various things in various contexts
(e.g., volume or assignments or ...).  I do not need to hover, select,
hyperlink, or otherwise reference the polygon in any way.  So, adding it as
a feature to the vector layer is not necessary [for me].  All I really need
is to color each of them one time when the map is loaded.


Can anyone tell me the best approach for this?  I have seen a lot of "hints"
at how to accomplish this; but no solutions yet.  E.g., I have seen SLD;
but, like with the technology, don't know a lot about this.  It looks like I
have to create a file to be posted to the map server.  I really need this to
be dynamic, as the context/colors may change between page loads.


Any help is greatly appreciated, especially code examples.


Sincerely,

Ivan



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