[GRASS-dev] Implementation of the High Pass Filter Additive Fusion technique (i.fusion.hpf)

[Nikos Alexandris]

Here it goes, as Nikos Ves (depending on free time) works on the Python version (and I'll try to 
help), the bash proof of concept works. Attached here.

After some initial testing, we think that GRASS' results are just slightly more smooth for when 
applying the exact same parameters to get the HPFA Pan-Sharpened material.

To run a test, get the attached tarred file, untar, compile as a grass-addon against G64. Then, 
the simplest execution form will be:

# note, the *algorithm* processes each low resolution image separately
i.fusion.hpf pan=lsat7_2000_80 msx=lsat7_2000_10

# or, let's get the usual landsat bands 1, 2 and 3
i.fusion.hpf pan=lsat7_2000_80 msx=lsat7_2000_10,lsat7_2000_20,lsat7_2000_30

# some manual work to rebalance colors (required)
i.landsat.rgb r=hpf_lsat7_2000_30 g=hpf_lsat7_2000_20 b=hpf_lsat7_2000_10
d.mon x0
d.rgb r=hpf_lsat7_2000_30 g=hpf_lsat7_2000_20 b=hpf_lsat7_2000_10

# increase crispness (not very obvious)
i.fusion.hpf pan=lsat7_2000_80 msx=lsat7_2000_10,lsat7_2000_20,lsat7_2000_30 --o 
modulator=max
i.landsat.rgb r=hpf_lsat7_2000_30 g=hpf_lsat7_2000_20 b=hpf_lsat7_2000_10
d.mon x1
d.rgb r=hpf_lsat7_2000_30 g=hpf_lsat7_2000_20 b=hpf_lsat7_2000_10

# hmmm... let's override the algorithms ratio computation
i.fusion.hpf pan=lsat7_2000_80 msx=lsat7_2000_10,lsat7_2000_20,lsat7_2000_30 --o 
modulator=max ratio=6
i.landsat.rgb r=hpf_lsat7_2000_30 g=hpf_lsat7_2000_20 b=hpf_lsat7_2000_10
d.mon x2
d.rgb r=hpf_lsat7_2000_30 g=hpf_lsat7_2000_20 b=hpf_lsat7_2000_10


BTW, it works really great with QuickBird imagery. Will upload in the next days screenshots 
with freely available HR imagery (i.e. QB2, IKONOS) and Landsat5, 7 and 8. Just a few Landsat 
8 screenshots uploaded in the Wiki:

http://grasswiki.osgeo.org/wiki/File:Bengkalis_Island_Landsat8_RGB_Red_NIR_Blue.jpg
http://grasswiki.osgeo.org/wiki/File:Bengkalis_Island_Landsat8_Panchromatic.jpg
http://grasswiki.osgeo.org/wiki/File:Bengkalis_Island_Landsat8_HPFA_Sharpened_RGB_Red_NI
R_Blue_Default_Parameters.jpg
http://grasswiki.osgeo.org/wiki/File:Bengkalis_Island_Landsat8_HPFA_Sharpened_RGB_Red_NI
R_Blue_Max_Crispness.jpg

Nikos
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