[mapserver-users] Selective Background Transparency with Labels

[Bill Thoen]

Is there a way to set a LABEL BACKGROUNDCOLOR to render transparent just 
pixels of a particular color instead of changing all pixels to the 
specified color? My situation is regarding contour line labels. I want 
the label to follow the contour line's center, but I would like just the 
parts of the contour line behind the labels to be knocked out, leaving 
the background otherwise untouched.  In this case the color of the layer 
just below the contour lines varies across the map (it's a shaded relief 
layer), so setting BACKGOUNDCOLOR to a specific value doesn't give me 
the effect I want. Any solutions?

 - Bill Thoen