[mapserver-users] Using PROCESSING SCALE and SCALE_BUCKETS parameters

[Dejan.Gambin at pula.hr]

Hi,

I hope someone has some experience with this:

I am classifying pixel values from a tiff file (converted from asc). The 
values are in range 0-100 and I need to clasify them in a following manner 
(don't bother the COLOR values :-):

  CLASS
    EXPRESSION ([pixel] <= 35)
    NAME '35dB(A)'
    COLOR 255 255 255
    TEMPLATE "void"
  END # Class
  CLASS
    EXPRESSION ([pixel] > 35 and [pixel] <=40)
    NAME '40dB(A)'
    COLOR 255 255 255
    TEMPLATE "void"
  END # Class
  CLASS
    EXPRESSION ([pixel] > 40 and [pixel] <=45)
    NAME '45dB(A)'
    COLOR 255 255 255
    TEMPLATE "void"
  END # Class
  CLASS
    EXPRESSION ([pixel] > 45 and [pixel] <=50)
    NAME '50dB(A)'
    COLOR 255 255 255
    TEMPLATE "void"
  END # Class
  CLASS
    EXPRESSION ([pixel] > 50 and [pixel] <=55)
    NAME '55dB(A)'
    COLOR 255 255 255
    TEMPLATE "void"
  END # Class
  CLASS
    EXPRESSION ([pixel] > 55 and [pixel] <=60)
    NAME '60dB(A)'
    COLOR 255 255 255
    TEMPLATE "void"
  END # Class
  CLASS
    EXPRESSION ([pixel] > 60 and [pixel] <=65)
    NAME '65dB(A)'
    COLOR 255 255 255
    TEMPLATE "void"
  END # Class
  CLASS
    EXPRESSION ([pixel] > 65 and [pixel] <=70)
    NAME '70dB(A)'
    COLOR 255 255 255
    TEMPLATE "void"
  END # Class
  CLASS
    EXPRESSION ([pixel] > 70 and [pixel] <=75)
    NAME '75dB(A)'
    COLOR 255 255 255
    TEMPLATE "void"
  END # Class
  CLASS
    EXPRESSION ([pixel] > 75 and [pixel] <=80)
    NAME '80dB(A)'
    COLOR 255 255 255
    TEMPLATE "void"
  END # Class
  CLASS
    EXPRESSION ([pixel] > 80)
    NAME '>80dB(A)'
    COLOR 255 255 255
    TEMPLATE "void"
  END # Class


Since this can be slow, can I make some performance improvements by using 
PROCESSING SCALE=min,max and SCALE_BUCKETS parameters? I have tried 
something like:

PROCESSING "SCALE=1,100"
PROCESSING "SCALE_BUCKETS=20"

but I didn't really see much difference. Is this OK? Is it enough anyway 
to add those two statements and leave the classes intact?

thanks very much

regards, dejan
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