[GRASSLIST:9613] Re: filtering with FFT

[Martin Landa]

Hi Markus,

> can you put a mini location somewhere to play?

the dataset which I use for lessons "Image processing" [1] (only in
Czech) at my university
is available at [2].

[1] http://gama.fsv.cvut.cz/wiki/index.php/Zpracov%C3%A1n%C3%AD_obrazov%C3%BDch_dat

[2]
http://grass.fsv.cvut.cz/~martin/vyuka/zzoz/datasety/

Best regards, Martin

PS: merry Christmas all GRASS developers/users...

>
> Markus
>
> On Mon, Dec 19, 2005 at 10:38:43PM +0100, Martin Landa wrote:
> > Hi all,
> >
> > according to OSS GIS: A GRASS GIS Approach (see page 243) I am trying
> > to apply high pass filter with FFT. I always get a strange result
> > image (see the attached file).
> >
> > g.region rast=tm1
> > i.fft in=tm1 real=tm1_r imag=tm1_i
> > g.region rast=tm1_r
> > r.circle -b out=ff coord=-769058,-988168 max=1550
> > r.mapcalc 'MASK=if(isnull(ff),1,null())'
> > i.ifft real=tm1_r imag=tm1_i out=tm1_hp
> > g.remove rast=MASK
> > g.region rast=tm1
> > r.colors map=tm1_hp col=grey.eq
> > d.rast tm1_hp
> >
> > I don't know where I am wrong ... Does anyone have the same problem?
> >
> > Thanks for help, best regards,
> >
> > Martin
>
>
>
> --
> Markus Neteler     <neteler itc it>       http://mpa.itc.it
> ITC-irst -  Centro per la Ricerca Scientifica e Tecnologica
> MPBA - Predictive Models for Biol. & Environ. Data Analysis
> Via Sommarive, 18        -       38050 Povo (Trento), Italy
>