Le 09/01/2025 à 20:27, Joe McGlinchy via gdal-dev a écrit :
Hello,
I'm wanting to pansharpen only a subset of multispectral bands I have
available. Say for instance I have blue-green-red-nir, and a
panchromatic band, I can calculate the relative weights to specify
when using `gdal_pansharpen` on the full multispectral dataset. If I
want to only pansharpen, for example, the red and NIR bands, is it
best to perform the pansharpening on the full dataset and only retain
the bands I need? Or can i provide only the weights specific to the
bands I want to pansharpen? If I can do the latter (which I can, given
the parameter set to `gdal_pansharpen`), do I need to recalculate
those weights, or only provide the subset of weights for those
specific bands?
Given the formula at
https://gdal.org/en/stable/drivers/raster/vrt.html#gdal-vrttut-pansharpen
pseudo_panchro[pixel] = sum(weight[i] * spectral[pixel][i] for i=0 to
nb_spectral_bands-1)
ratio = panchro[pixel] / pseudo_panchro[pixel]
for i=0 to nb_spectral_bands-1:
output_value[pixel][i] = input_value[pixel][i] * ratio
if you only provide a subset of the input spectral bands, you won't be
able to reconstruct a plausible pseudo_panchro values, hence the scaling
ratio will not be accurate.
If your spectral dataset has bands in the R,G,B,NIR order, you can
achieve what you want with:
$ gdal_pansharpen panchro.tif rgbnir.tif,band=1 rgbnir.tif,band=2
rgbnir.tif,band=3 rgbnir.tif,band=4 out.tif -b 1 -b 4
Even
--
http://www.spatialys.com
My software is free, but my time generally not.
Butcher of all kinds of standards, open or closed formats. At the end, this is
just about bytes.
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