| miracle of !order [message #42656] |
Sat, 19 February 2005 04:10  |
R.Bauer
Messages: 1424
Registered: November 1998
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Senior Member |
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Dear all
probably this is already known, but there is some risk to do something wrong
so I like to note it here. Probably David likes to put it on his marvellous
page.
I came to a problem reading and processing an image. If I have used the
default !order=0 all goes right while it wasn't possible to read the text
on the image so I switched to !order=1. Then a journey starts to understand
why all was a bit wrong.
I try to decribe the situation.
We have a circular pattern nearly in the center of a 1024x1024 image. To
compare all the images the pattern must be aligned. First we detected the
center of the circle and then we could do the alignment by rotating the
image around this center point. This was done in a widget by displaying the
image. The widget is used for selecting the center of the circle and some
other things. With !order=0 all goes right.
Then I switched to !order=1 and the results where different. It takes some
time to understand what goes wrong.
If you use !order=1 only the image on screen got's reordered. The function
which I used to rotate (rot) the data of the image does not recognice this
Sysvar set to 1 and it rotates the image not reordered.
The center point was wrong.
If you like to have reordered data on display and you like to do something
else with this image data then you should reorder it yourself. !order=0
should not be changed. That's the only way to use the right data in all
your routines.
cheers
Reimar
--
Forschungszentrum Juelich
email: R.Bauer@fz-juelich.de
http://www.fz-juelich.de/icg/icg-i/
============================================================ ======
a IDL library at ForschungsZentrum Juelich
http://www.fz-juelich.de/icg/icg-i/idl_icglib/idl_lib_intro. html
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| Re: miracle of !order [message #42744 is a reply to message #42656] |
Sun, 20 February 2005 17:11  |
David Fanning
Messages: 11724
Registered: August 2001
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Senior Member |
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Reimar Bauer writes:
> probably this is already known, but there is some risk to do something wrong
> so I like to note it here. Probably David likes to put it on his marvellous
> page.
>
> I came to a problem reading and processing an image. If I have used the
> default !order=0 all goes right while it wasn't possible to read the text
> on the image so I switched to !order=1. Then a journey starts to understand
> why all was a bit wrong.
I agree. As soon as you allow an ORDER keyword into
any IDL program you write, you have opened up Pandora's Box.
If anyone ever suggests it in your presence in conjunction
with the words "draw widget" or "GUI", immediately leave
the room. You want nothing more to do with that person!
It will ruin your life, or -- at the very least -- give
you such severe migraine headaches that you will rue the
day you first heard the word "IDL" spoken. (I realize
this is not the *only* cause of this condition, but this
will surely do it.)
If you want to image flipped top to bottom, flip the
damn thing yourself (with the ROTATE command) and forget
you ever read the word "ORDER" in association with a TV
command. You will thank me for a long, long time. :-)
Cheers,
David
--
David Fanning, Ph.D.
Fanning Software Consulting, Inc.
Coyote's Guide to IDL Programming: http://www.dfanning.com/
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