[mapserver-users] Specify NODATA for 3 bands?

[Gregor at HostGIS]

Hey guys.

I have some NAIP imagery in MrSID format. It displays, but the black 
area where counties meet is really ugly. The MrSIDs are 3 one-byte 
bands: R/G/B The bands do not specify a NODATA but I figure that 0/0/0 
(all black) may be usable as a NODATA value, via a PROCESSING directive.

It works nicely, suppressing the black halos and making the 
almost-seamless effect where the counties intersect. BUT... it only does 
so if I don't show all 3 bands. If I specify any combination of BAND 
directives, I get a greyscale image (of course) and the NODATA works 
(black halos are gone, so counties are near seamless).
    PROCESSING "NODATA=0"
    PROCESSING "BANDS="1,2"
    #PROCESSING "BANDS="3"
    #PROCESSING "BANDS="1,3"

But, if I do not specify the BAND or if I specify all 3 bands, I get the 
black halos as if the NODATA were not specified. What gives? Is there 
something special I must do to have the NODATA take effect for 3 or more 
bands?

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