[GRASS-dev] GRASS-dev] On i.histo.match (Re: On (Landsat) imagery naming patterns)

[Nikos Alexandris]

On Thursday 01 of August 2013 13:42:03 Moritz Lennert wrote:
> On 01/08/13 13:43, Nikos Alexandris wrote:
> > Michael:
> >>>>>> What about just using r.rescale to rescale this?
> > 
> > Nikos:
> >>>>> Already tried (in the past) and I don't think it works from DCELL>
> >>>>> 8-bit. It seems to chew-up (silently, as Moritz mentioned I think
> >>>>> among
> >>>>> the lines in ticket #2^11) values.
> >>>>> 
> >>>>> It seems that "integerising" manually, in this case, is the best
> >>>>> approach. With the essential question remaining on "how many fine
> >>>>> digits
> >>>>> should be preserved?".
> > 
> > Moritz:
> >>>> r.rescale is just a frontend to r.reclass. and as such is meant for
> >>>> CELL
> >>>> maps. It should'nt make a difference whether it is 8-bit or more,
> >>>> though.
> >>>> For DCELL you can try to use r.recode.
> > 
> > Nikos:
> >>> Didn't work also (tried the previous days) -- I can try again.
> > 
> > Moritz:
> >> Please be more precise than "didn't work"...
> > 
> > Right, "be more precise" is the key to "freedom" :D.  Indeed, I used to
> > say
> > (either in a "rules" file, or directly using "...<<  EOF"
> > 
> > 0.0:1.0:0:255
> > 
> > This did not work.  Both stats and histogram of the recoded raster map,
> > e.g. a Red-Reflectance image ranging in
> > 
> > r.info Red_ToAR -r
> > 
> > min=0
> > max=0.774115699104528
> > 
> > were kinda flattened out
> > 
> > r.stats Red_ToAR_recoded_255
> > 
> >   100%
> > 
> > 0
> > 255
> > 
> > Looking at the image I want to recode
> > 
> > r.stats Red_ToAR | head
> > 
> >   100%
> > 
> > 0-0.003036
> > 0.02125-0.024286
> > 0.024286-0.027322
> > 0.027322-0.030357
> > 0.030357-0.033393
> > 0.033393-0.036429
> > 0.036429-0.039465
> > 0.039465-0.0425
> > 0.0425-0.045536
> > 0.045536-0.048572
> > 
> > I altered the rules file like
> > 
> > 0.001:1.0:0:255
> > 
> > 
> > This works-out!  Now, the recoded image is
> > 
> > r.recode in=Red_ToAR out=Red_ToAR_recoded_255 rules=recode_rules  --o
> > r.stats Red_ToAR_recoded_255
> > 
> >   100%
> > 
> > 5
> > 6
> > 7
> > .
> > ..
> > ...  \
> > ....>  Many values in-between
> > ...  /
> > ..
> > .
> > 195
> > 196
> > 197
> > *
> > 
> > And the histogram looks "nice" as well. I didn't grasp that -- from where
> > should I?  In the manual there is only an example from int to float
> > (however, indeed, instructing 0.1 as the "target" min value).
> 
> There does seem to be a bug in r.recode. Your first rule set should work
> if you set the -d flag. Maybe you can file a ticket ?


Oh man... I need to rest.  The "-d" flag... that's it :-p

Nikos  (learning every day new stuff :-)).