[mapserver-users] set COLOR to transparent?

[Lime, Steve D (DNR)]

Not sure if this will work or not. The OFFSITE parameter is normally used with rasters to set pixel transparency. You could try something like:

  OFFSITE 1 2 3
  CLASS
    EXPRESSION ...
    COLOR 1 2 3
  END

I don't know if the raster code looks for offsite pixels before *or* after classification. Still might have the reseting problem. I agree that this
is a desirable piece of functionality. Frank would know for sure what's possible in 5.6...

Steve

________________________________________
From: mapserver-users-bounces at lists.osgeo.org [mapserver-users-bounces at lists.osgeo.org] On Behalf Of Wendell Turner [wendell at enflight.com]
Sent: Friday, April 30, 2010 4:34 PM
To: mapserver-users at lists.osgeo.org
Subject: [mapserver-users] set COLOR to transparent?

Is there a way to turn a pixel transparent?  That is,
something like:

 CLASS
  EXPRESSION ([red] > 200 AND [green] > 200 AND [blue] > 200 )
  TRANSPARENT
 END

Or is there a way to set the pixel to the index of the
transparent entry in the color table?

Also, is there an 'ELSE' clause to the class/expression
statements?  That is, if the expression fails, leave other
pixels alone.  Using a class and an expression seems to
reset all other pixels.

Thanks,

Wendell

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