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https://github.com/nikosalexandris/i.fusion.hpf.sh
Replication of the High-Pass Filter Addition Image Fusion for GRASS-GIS (bash script)
https://github.com/nikosalexandris/i.fusion.hpf.sh
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Replication of the High-Pass Filter Addition Image Fusion for GRASS-GIS (bash script)
- Host: GitHub
- URL: https://github.com/nikosalexandris/i.fusion.hpf.sh
- Owner: NikosAlexandris
- Created: 2014-10-23T22:48:27.000Z (about 10 years ago)
- Default Branch: master
- Last Pushed: 2014-12-02T23:11:48.000Z (almost 10 years ago)
- Last Synced: 2023-12-13T10:05:52.158Z (11 months ago)
- Language: Shell
- Size: 12.8 MB
- Stars: 1
- Watchers: 2
- Forks: 0
- Open Issues: 1
-
Metadata Files:
- Readme: README.md
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README
`i.fusion.hpf` is a GRASS-GIS module to combine high-resolution
panchromatic data with lower resolution multispectral data, resulting in an
output with both excellent detail and a realistic representation of original
multispectral scene colors.
The process involves a convolution using a High Pass Filter (HPF) on the high
resolution data, then combining this with the lower resolution multispectral
data.
Optionally, a linear histogram matching technique is performed in a way that
matches the resulting Pan-Sharpened imaged to them statistical mean and standard
deviation of the original multi-spectral image.
Source: Gangkofner, 2008
Algorithm description
=====================
1. Computing ratio of low (Multi-Spectral) to high (Panchromatic) resolutions
2. High Pass Filtering the Panchromatic Image
3. Resampling MSX image to the higher resolution
4. Adding weighted High-Pass-Filetred image to the upsampled MSX image
5. Optionally, matching histogram of Pansharpened image to the one of the
original MSX image
Installation
============
Requirements
------------
see [GRASS Addons SVN repository, README file, Installation - Code Compilation](https://svn.osgeo.org/grass/grass-addons/README)
Installation steps
------------------
Making the script `i.fusion.hpf` available from within any GRASS-GIS ver. 6.4 session, may be done via the following steps:
1. launch a GRASS-GIS’ ver. 6.4 session
2. navigate into the script’s source directory
3. execute `make MODULE_TOPDIR=$GISBASE`
Usage
=====
After installation, from within a GRASS-GIS session, see help details via `i.fusion.hpf --help` -- also provided here:
```
Description:
Fuses a High-Resolution Panchromatic with its corresponding Low Resolution Multi-Spectral image based on the High-Pass Filter Addition technique
Keywords:
imagery, fusion, HPF, HPFA
Usage:
i.fusion.hpf [-l2] pan=string msx=string[,string,...]
outputprefix=string [ratio=value] [center=string] [center2=string]
[modulator=string] [modulator2=string] [--verbose] [--quiet]
Flags:
-l Linearly match histograms of the HPF Pan-sharpened output(s) to the Multi-Spectral input(s)
-2 2-Pass Processing (recommended) for large Resolution Ratio (>=5.5)
--v Verbose module output
--q Quiet module output
Parameters:
pan High resolution panchromatic image
msx Low resolution multi-spectral image(s)
outputprefix Prefix for the Pan-Sharpened Multi-Spectral image(s)
default: hpf
ratio Custom defined ratio to override standard calculation
options: 1-10
center Center cell value of the High-Pass-Filter
options: low,mid,high
default: low
low: Low center cell value
mid: Mid center value
high: High center value
center2 Center cell value for the second pass of the High-Pass-Filter
options: low,mid,high
default: low
low: Low center cell value
mid: Mid center value
high: High center value
modulator Level of modulating factor weighting the HPF image to determine crispness
options: min,mid,max
default: mid
min: Minimum modulating factor
mid: Mid modulating factor
max: Maximum modulating factor
modulator2 Level of modulating factor weighting the HPF image in the second pass to determine crispness
options: min,mid,max
default: mid
min: Minimum modulating factor (0.25) for the 2nd pass
mid: Mid modulating factor (0.35) for the 2nd pass
max: Maximum modulating factor (0.5) for 2nd pass
```
Implementation
==============
- started on 29. October 2013 | working state reached on 07. November 2013
- bash script for GRASS-GIS ver. 6.4
- easy converting for GRASS-GIS ver. 7
- should be easy to convert into Python
- needless to say, badly implemented by a non-programer!
Remarks
-------
- currently requires manual color rebalancing (e.g. by using i.landsat.rgb)
- easy to use, i.e.:
* for one band `i.fusion.hpf pan=Panchromatic msx=${Band}`
* for multiple bands `i.fusion.hpf pan=Panchromatic msx=Red,Green,Blue,NIR`
- easy to test various parameters that define the High-Pass filter’s *kernel
size* and *center value*
- should work with **any** kind of imagery (think of bitness)
To Do
-----
1. ~~convert to Python script~~
2. integrate in `i.pansharpen`? Checking options...
2. ~~automatic looping over multiple Multi-Spectral images so as to render
needless the task for manual loops~~
3. ~~linear histogram matching option (as explained in the related
publication)~~ *Does it work properly?*
4. ~~works only for integers – with minor tweaking it can work with
`r.mfilter.fp` to crunch Floating Points as well~~
5. consider [Have backticks (i.e. `cmd`) in *sh shells been deprecated?](http://unix.stackexchange.com/q/126927/13011)
6. what about [Why should eval be avoided in Bash, and what should I use instead?](http://stackoverflow.com/q/17529220/1172302)
7. identically named pan-sharpened images won't be overwritten -- advice to use `--o Allow output files to overwrite existing files` <- needs to be shown while `i.fusion.hpf --help`!
Questions
---------
- Utilise the existing histogram matching code in `i.pansharpen`?
It performs histogram matching using the Standard Deviation and Mean of the
reference image.
References
==========
Gangkofner, U. G., Pradhan, P. S., and Holcomb, D. W. (2008). Op-
timizing the high-pass filter addition technique for image fusion.
PHOTOGRAMMETRIC ENGINEERING & REMOTE SENSING,
74(9):1107–1118.