Running C:\bin\bb2.pl   Sun Dec 13 16:30:19 2015
Unique colors=27.645898M =  76.471%  <<< EXACT!

SE: Sum of Event Times = 6.789 min, now-init = 6.78937 min
ETime=239.024 ms =  0.059%, 1 Hits, Event 'PerlMagic Read Raw File'
ETime=  6.785 min = 99.941%, 1 Hits, Event 'Quantize'
99.94% -> Quantize
 0.06% -> PerlMagic Read Raw File
Elapsed C:\bin\bb2.pl time = 6.789 min


# Here is the hash way implemented by ImageMagick Bone-Nary[*]:
Running C:\bin\bb.pl   Sun Dec 13 15:19:29 2015;  
Conv convert.exe -size 7360x4912 -depth 16 \
RGB:i:/exp/raw/pf-2015.0531-249465.pprgb.7360x4912.raw \
-unique-colors \
i:/exp/raw/pf-2015.0531-249465.pprgb.7360x4912.raw.tif ->
        size=165875652
Elapsed C:\bin\bb.pl time = 6.936 min

I:\exp\raw>mult 165875652 /27645898
6.0000    <<  Very close agreement on Unique Count

I:\exp\raw>mult 6.936 60 /0.946
439.915433