Re: [Geoserver-users] Bitwise operators in SLD files

[Justin D. <jde...@op...>]

Hi Richard,

I do not believe there is anything in the Filter spec directly which
will support this. However with a little bit of coding you should be
able to achieve this with filter functions. For instance.

<Filter>
  <PropertyIsEqualTo>
    <Function name="bitwiseAnd">
       <PropertyName>attributes</PropertyName>
       <Literal>0a</Literal>
    <Function>
    <Literal>0a</Literal>
  </PropertyIsEqualTo>
</Filter>

To pull this off you would have to implement the "bitewiseAnd" function
at the geotools level. An implementation might look something like:

class BitwiseAndFunction extends
org.geotools.filter.FunctionExpressionImpl {

  public BitwiseAndFunction() {
    super("bitwiseAnd");
  }

  public int getArgCount() {
     return 2;
  }

  public Object evaluate( Object feature ) {
     //get the value of attribute as an integer
     Integer value = getExpression(0).evaluate(feature, Integer.class);

     //get the string value of the mask
     String mask = getExpression(1).evaluate(null);

     //convert the mask to int
     int intMask = Integer.parseInt( mask, 16 ):

     return Integer.toHexString( value.intValue() & intMask );
  }
}

This is just a crack off the top of my head so I am sure it will not
work as written :), but the general strategy holds.

Hopefully this makes sense. If you have any more questions or anything
is unclear please don't hesitate to ask.

-Justin

Shaw, Richard A wrote:
> Does anybody know if it is possible to have bitwise operator in SLD files ?
> 
> I hve the following data
> 
> Geom, attributes
> 
> Where attributes is an integer containing bit values as follows -
> 
> 0x01 - motorway
> 0x02 - a road
> 0x04 - b road
> 0x08 - single carriageway
> 0x10 - dual carriageway
> 
> I want to draw dual carriageway A roads in dark green and single carriageway A roads in light green -
> 
> ((attributes & 0x0a) == 0x0a)    use dark green
> ((attributes & 0x12) == 0x12)	 use light green
> 
> 
> Richard Shaw
> 
> ¤º°`°º¤ø,¸¸,ø¤º°`°º¤ø¤º°`°º¤ø,¸¸,ø¤º°`°º¤ø¤º°`°º¤ø,¸¸,ø¤
> 
> Richard Shaw  
> Technical Design Authority - Information Solutions Consultancy  
> Intelligent Transport Systems 
> 
> Atkins Highways and Transportation 
> Woodcote Grove, Ashley Road, Epsom, Surrey, KT18 5BW
> 
> Tel: +44 (0) 1372 756407 
> Fax: +44 (0) 1372 740055
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> 
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> 
> 
> 
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-- 
Justin Deoliveira
The Open Planning Project
jde...@op...