| FFT-filtering [message #15043] |
Fri, 16 April 1999 00:00  |
Harald von der Osten-
Messages: 15
Registered: February 1999
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Junior Member |
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Dear IDL-specialists,
I would like to do some FFT-filtering on TIFF-files in IDL. Does such
routines still exist? Where could I find some code?
It would be great if one could manually change/delete via cursor areas
in the frequency-domain before transfering the data back into the
time-domain
Thanks a lot for any (maybe: positive??) answer
Harald
--
Harald von der Osten-Woldenburg
Geophysical Prospection of Archaeological Sites
Landesdenkmalamt Baden-Wuerttemberg
Silberburgstrasse 193
D-70178 Stuttgart
http://delos.lf.net/~hvdosten/index.html: Geomagnetics and Geoelectrics
http://www.region-lb.de/HomeSites/HvdOsten: Ground Penetrating Radar and
EMI
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| Re: FFT-filtering [message #15121 is a reply to message #15043] |
Tue, 20 April 1999 00:00  |
wbiagiot
Messages: 59
Registered: January 1999
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Member |
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> Dear IDL-specialists,
>
> I would like to do some FFT-filtering on TIFF-files in IDL. Does such
> routines still exist? Where could I find some code?
>
> It would be great if one could manually change/delete via cursor areas
> in the frequency-domain before transfering the data back into the
> time-domain
>
> Thanks a lot for any (maybe: positive??) answer
>
> Harald
Harald,
One hint that I could give you is one that I made good use of myself. On his
website, David Fanning provides IDL source code for an IDL "rubberband" box
(click and stretch) that I made very good use of. I provided some extensions
around it (widgets for nudging the final line coordinates) to make it more
usable. By drawing your TIFF file and manually drawing a r-band box, you've
selected the region of your image that you wish to act upon. Extract the
data selection into another matrix, FFT-it, filter it, inverse FFT-it and
place it back into the original matrix. The IDL demos perform this operation
on an entire image and that source code (provided with IDL) is a good place
to look.
Granted this is highly simplified, but provides the basic blocks to tackle.
You could also skip the rubberband box code and just use sliders for
specifying the box.
Thanks to David for the /pixmap lesson.
-Bill B.
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