[mapserver-users] layer classification with MapScript

[Brent Fraser]

Puneet,

   If you don't care about mapserver generating a legend graphic, you 
could use mapserver CGI's ability (no scripting required) to do 
attribute binding (get values from a feature's attribute values).  I've 
used a single class def of:

         CLASS
             STYLE  # Line, Poly and Point outline
                 SYMBOL       [sSymbol]
                 OUTLINECOLOR [sOutlineColor]
                 COLOR        [sColor]
                 SIZE         [sSize]
             END
             TEXT ([Label])
             LABEL
                 ANGLE AUTO
                 POSITION UR
                 COLOR [lColor]
                 OUTLINECOLOR [lOutlineColor]
                 TYPE truetype
                 FONT 'Arial'
                 SIZE [lSize]
             END
         END

where the data/connection accessed a view joining the feature table to a 
class table where the styling values were defined.  And you need 3 layer 
defs, one for points, lines and polygons.   But using this technique, 
there is no way to get a legend graphic show all the classes.

   So in your PHP code you would need to do a  generic database query to 
get a set of classes, then for each row create a class object and add it 
to the layer object.  Then have mapscript process the features and 
render a map image by doing a draw() (and a legend graphic by doing a 
drawLegend()).  Or, as others have suggested,  you could pass an SLD to 
mapserver via WMS and request a legend graphic.

Best Regards,
Brent Fraser


On 8/27/2011 5:02 PM, Mr. Puneet Kishor wrote:
> I have a layer classification issue. I want to do something along the lines of (semi-pseudocode ahead) --
>
>      $layerObj->{data} = 'the_geom FROM (SELECT gid, the_geom, class_name, class_color FROM table) t USING UNIQUE gid';
>      $layerObj->{classitem} = 'class_name';
>
>      while (my $row in $layerObj->{data}) {
>          create class with 'name = class_name', 'expression = class_name', 'color = class_color'
>      }
>
> How do I iterate over the rows retrieved from the table in order to create classes? I don't see any obvious reference to a db result set._______________________________________________
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