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

[Michael Barton]

On Nov 16, 2013, at 5:46 PM, Nikos Alexandris <nik at nikosalexandris.net>
 wrote:

> "	Replying to cmbarton:
> 	If you have an image set that is more than 8bit, I can use it to test some 	
> 	things. i.histo.match is a nice module. But its objective is different from 
> 	histogram matching in i.pan.sharpen. So it would need modification to be 		
> 	used in this context. When I was writing i.pan.sharpen, I looked at the 		
> 	i.histo.match code but it was easier to use a much simpler algorithm. But 	
> 	since you know i.histo.match maybe you can see where the code could be 		
> 	modified to be used in i.pan.sharpen.
> 
> Your histogram matching code matches the histogram of a source image to that 
> of a target image, whereas i.histo.match matches the histogram of each given 
> image to the cumulative histogram of all images. Both approaches are valid, 
> and both should be available in a histogram matching module.   "

I also looked at i.histo.match when I was writing i.pansharpen. IIRC, its original goal was to create an average histogram that could be applied to multiple images tiled together, so that they would have a nice consistent appearance without patching them into a single image. It is not the kind of histogram matching needed for pan sharpening, however. 

I do not have an image set that is >8bit and floating point for testing. But someone on the list did not too long ago.

Any histogram matching algorithm (including a variant of i.histo.match) could be added as a drop-in method to i.pansharpen. All it needs is to take an "original" and "target" input files (the target is the file whose histogram is modified to match the original), and a "matched" output file. 

Michael


> 
> 
>> There I don't see a 8bit limitation (I may be wrong). This might solve
>> ticket #2048.
> 
> Note, the IHS method for example depends on the respective modules which are 
> 8-bit based too if I am not wrong.
> 
> Nikos



____________________
C. Michael Barton
Director, Center for Social Dynamics & Complexity 
Professor of Anthropology, School of Human Evolution & Social Change
Arizona State University

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