I haven't had time today to look into this. I used a fairly standard histogram matching algorithm, for which I cited the reference. But I don't remember exactly how it went. Matching the SD was not part of it however.
Michael ______________________________ C. Michael Barton Director, Center for Social Dynamics & Complexity Professor of Anthropology, School of Human Evolution & Social Change Arizona State University Tempe, AZ 85287-2402 USA voice: 480-965-6262 (SHESC), 480-965-8130/727-9746 (CSDC) fax: 480-965-7671(SHESC), 480-727-0709 (CSDC) www: http://csdc.asu.edu, http://shesc.asu.edu http://www.public.asu.edu/~cmbarton On Nov 15, 2013, at 3:20 AM, Moritz Lennert <[email protected]> wrote: > On 15/11/13 10:50, Nikos Alexandris wrote: >> Nikos Alexandris wrote: >> >> > > together with Nikos Ves, we share the "i.fusion.hpf" idea/proof of >> >> > > concept. At the moment, we have a custom shell script named >> >> > > `i.fusion.hpf` (an attempt for a proper GRASS add-on), which implements >> >> > > the High Pass Filter Additive (HPFA) Fusion Technique for >> Pan-Sharpening >> >> > > [*]. Nikos V started already porting to Python. How can we proceed in >> >> > > sharing it? >> >> > >> >> > [...] >> >> > >> >> > > Two questions >> >> > > >> >> > > ? Can someone confirm that the part of the existing "i.pansharpen" code >> >> > > that performs histogram matching (code lines 348 - 431), do so as >> >> > > "linearly stretching an image to match another image's Mean and >> StdDev"? >> >> Moritz Lennert: >> >> > AFAICT, it applies the method described in [1]. >> >> Is that a reference also indicated in i.pansharpen's manual? > > It's not in the manual, but there's a long list of other references. But > Michael is the one who knows where the inspiration came from. AFAIK, this is > the classical, generic method of histogram matching. > >> >> > I don't know (and don't have the time to think about) what this >> method does >> >> > in terms of mean and stddev. >> >> My guess was/is that it is not the same, i.e. it does not match Mean and >> StdDev. As a quick test, I tried the identical (me thinks) tool in >> WhiteboxGIS "Histogram Matching (Two Images)", does not give identical >> Means and StdDevs after the operation -- which is the case with >> i.pansharpen too if I am not wrong. >> > > I just did a quick test: > > pan in: > > mean: 31.813 > standard deviation: 3.75447 > > ms in: > > mean: 15.2307 > standard deviation: 3.55858 > > pan out: > > mean: 15.6117 > standard deviation: 3.23408 > > So for this example, mean seems to have been adjusted, but stddev not. > >> > > ? Would it be desired to get the HPFA algorithm integrated in >> >> > > i.pansharpen? >> >> > >> >> > Yes. I think that if we have a generic module such as i.pansharpen, it >> >> > would be preferable to have all pansharpening methods in that one module. >> >> There is one "difference" in that HPFA treats all bands to be sharpened >> separately. And, in this manner, it can be (mis-)used to sharpen any >> low-res band. For example, WorldView-2 products have 8 multi-spectral >> bands. Hence the "not red= green= blue=" design so far from my side. > > i.pansharpen does not imply rgb either (although the description of the ms* > parameters does suggest that. You can obviously use any ms bands you want. > > Moritz _______________________________________________ grass-dev mailing list [email protected] http://lists.osgeo.org/mailman/listinfo/grass-dev
