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NAME

i.fusion.hpf - Fusing high resolution panchromatic and low resolution multi-spectral data based on the High-Pass Filter Addition technique (Gangkofner, 2008).

KEYWORDS

imagery, fusion, sharpening, high pass filter, HPFA

SYNOPSIS

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

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
--overwrite
Allow output files to overwrite existing files
--help
Print usage summary
--verbose
Verbose module output
--quiet
Quiet module output
--ui
Force launching GUI dialog

Parameters:

pan=filename [required]
High resolution Panchromatic image
msx=filename(s)[,filename(s),...] [required]
Low resolution Multi-Spectral image(s)
suffix=suffix string [required]
Suffix for output image(s)
Names of Pan-Sharpened image(s) will end with this suffix
Default: hpf
ratio=rational number
Custom ratio
Custom ratio overriding standard calculation
Options: 1.0-10.0
center=string
Center cell value
Center cell value of the High-Pass-Filter
Options: low, mid, high
Default: low
center2=string
2nd Pass center cell value
Center cell value for the second High-Pass-Filter (use -2 flag)
Options: low, mid, high
Default: low
modulation=string
Modulation level
Modulation level weighting the HPF image determining crispness
Options: min, mid, max
Default: mid
modulation2=string
2nd Pass modulation level (use -2 flag)
Modulation level weighting the second HPF image determining crispness (use -2 flag)
Options: min, mid, max
Default: mid
min: Minimum: 0.25
mid: Mid: 0.35
max: Maximum: 0.5
trim=rational number
Trimming factor
Trim output border pixels by a factor of the pixel size of the low resolution image. A factor of 1.0 may suffice.

Table of contents

DESCRIPTION

i.fusion.hpf is an implementation of the High Pass Filter Additive (HPFA) Fusion Technique. It combines 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 image to the statistical mean and standard deviation of the original multi-spectral image.

Background

  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
Figure:
 ____________________________________________________________________________
+                                                                            +
| Pan Img ->  High Pass Filter  ->  HP Img                                   |
|                                      |                                     |
|                                      v                                     |
| MSx Img ->  Weighting Factors ->  Weighted HP Img                          |
|       |                              |                                     |
|       |                              v                                     |
|       +------------------------>  Addition to MSx Img  =>  Fused MSx Image |
+____________________________________________________________________________+

Source: Gangkofner, 2008

NOTES

EXAMPLE

The module is fairly easy to use. Arbitrary examples: Pansharpening of one band:
i.fusion.hpf pan=Panchromatic msx=Red

Pansharpening of multiple bands:

i.fusion.hpf pan=Panchromatic msx=Red,Green,Blue,NIR

Various illustrated examples detailed in the document i.fusion.hpf, implementation of the High Pass Filter Additive (HPFA) Image Fusion Technique (PDF)

TODO

REFERENCES

SEE ALSO

i.pansharpen

AUTHORS

Nikos Alexandris
Panagiotis Mavrogiorgos

Last changed: $Date: 2018-08-22 09:41:47 +0200 (Wed, 22 Aug 2018) $

SOURCE CODE

Available at: i.fusion.hpf source code (history)


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