[GRASS-dev] On integrating i.fusion.hpf into i.pansharpen

[Nikos Alexandris]

Dear all,

I want to integrate the "AHPF" fusion algorithm, <i.fusion.hpf> [0], 
into <i.pansharpen> [1]. And I need some assistance.


1. <i.pansharpen> has the following, simple, interface:

i.pansharpen [-sl] red=name green=name blue=name pan=name
    output=basename method=value [--overwrite] [--help] [--verbose]
    [--quiet] [--ui]

plus

Flags:
   -s   Serial processing rather than parallel processing
   -l   Rebalance blue channel for LANDSAT


while the HPF implementation looks like:

i.fusion.hpf [-l2c] pan=filename msx=filename(s)[,filename(s),...]
    outputsuffix=suffix string [ratio=rational number] [center=string]
    [center2=string] [modulation=string] [modulation2=string]
    [trim=rational number] [--overwrite] [--help] [--verbose] [--quiet]
    [--ui]

plus

Flags:
   -l   Linearly match histogram of Pan-sharpened output to 
Multi-Spectral input
   -2   2-Pass Processing (recommended) for large resolution ratio 
(>=5.5)
   -c   Match color table of Pan-Sharpened output to Multi-Spectral 
input


While the first module appears to be simple and straightforward, it has 
its limitations (rgb required, underlying ihs method restricted to 8-bit 
data). The second module appears complex, but it works right away by 
simply feeding a pan and a multi-spectral band (or bands) and, offers 
many fine-tuning options.

2. <i.pansharpen> has the R-G-B logic hardcoded (one pan and three 
multi-spectral bands required), while <i.fusion.hpf> will work simply 
with a pan and only one or any number of multiple low-resolution bands.

If all of the fine-tuning options for HPF will be merged into 
i.pansharpen, it'll get "heavy" and complex.  I am asking for help to 
design the integration (not for the actual coding).  Any ideas?


Thank you, Nikos


--
[0] <https://github.com/NikosAlexandris/i.fusion.hpf>
[1] <http://grass.osgeo.org/grass70/manuals/i.pansharpen.html>