MapServer LAYER>CLASS>EXPRESSION Object

For more information on the use of EXPRESSIONs please refer to the MapServer Documentation.

With a CLASSITEM

If you wish to use more complicated styles for say OS MasterMap layers then you can use the following which will colour according to the value of a field name using EXPRESSION. It is also advisable to have a CLASS entry at the bottom of the list as a “catch all” style for the layer:

POLYGON – OS MasterMap GoLoader

CLASSITEM "OSMMSTYLE_NAME"
CLASS
     EXPRESSION "buildingFill"
     STYLE
         COLOR 255 204 153
         OUTLINECOLOR 204 204 204
     END
END
CLASS
     EXPRESSION "multipleSurfaceFill"
     STYLE
         COLOR 255 255 204
         OUTLINECOLOR 204 204 204
     END
END
CLASS
     EXPRESSION "0001 Building outline"
     STYLE
         COLOR 0 0 0
         WIDTH 2
   	 END
END

POLYGON – OS MasterMap TranspOSe / SuperpOSe

CLASSITEM "Legend"
CLASS
     EXPRESSION "0321 Building"
     STYLE
         COLOR 255 204 153
         OUTLINECOLOR 204 204 204
     END
END
CLASS
     EXPRESSION "0385 Nonconiferous - scattered"
     STYLE
         COLOR 0 0 0
         OUTLINECOLOR 204 204 204
         SYMBOL "0385Scattered" #[Draws a bitmap fill type]
     END
END

POLYLINE – OS MasterMap GoLoader

CLASSITEM "OSMMSTYLE_NAME"
CLASS
     EXPRESSION "defaultTopographicLine"
     STYLE
         COLOR 102 102 102
     END
END
CLASS
     EXPRESSION "buildingLine"
     STYLE
         COLOR 0 0 0
         WIDTH 2
     END
END

POLYLINE – OS MasterMap TranspOSe / SuperpOSe

CLASSITEM "Legend"
CLASS
      EXPRESSION "0030 Obstructing feature"
      STYLE
         COLOR 102 102 102
      END
END
CLASS

      EXPRESSION "0001 Building outline"
      STYLE
         COLOR 0 0 0
         WIDTH 2
      END
END

With a LABELITEM

GoLoader holds text as lines that require labeling.

LABELITEM - GoLoader

LABELITEM "TEXTSTRING"
#LABELANGLEITEM "OGR:LabelAngle"
MINSCALE 1
MAXSCALE 4000
#REQUIRES "![Aerial]"
#STYLEITEM "auto"
CLASSITEM "FEATURECODE"
CLASS
      EXPRESSION ([FEATURECODE] == 10026 OR [FEATURECODE] == 10166 OR [FEATURECODE] == 10178 OR [FEATURECODE] == 10184)
      LABEL
         FONT "arial"
         TYPE TRUETYPE
         ANTIALIAS TRUE
         COLOR 0 0 0
         OUTLINECOLOR 230 230 230
         SIZE 7
         POSITION cc
         ANGLE AUTO
      END
END
CLASS
      EXPRESSION ([FEATURECODE] == 10033)
      LABEL
         FONT "arialbd"
         TYPE TRUETYPE
         #ANTIALIAS TRUE
         COLOR 153 153 153
         #OUTLINECOLOR 255 255 255
         SIZE 15
         POSITION cc
         ANGLE AUTO
      END
END

TranspOSe / SuperpOSe holds text as an annotation layer therefore no labeling is required.

ANNOTATION – TranspOSe / SuperpOSe

LAYER
      NAME CartoText
      TYPE ANNOTATION 
      STATUS DEFAULT
      CONNECTIONTYPE OGR
      CONNECTION "Base/MasterMap/Carto_Text.TAB"
      MINSCALE 1
      MAXSCALE 6000
      STYLEITEM "auto"
      CLASS
      END
END