| Re: Zoom out of astronomical image preserving header info [message #42611] |
Thu, 17 February 2005 10:51  |
mperrin+news
Messages: 81
Registered: May 2001
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burkina <stebia@inwind.it> wrote:
> Ciao,
>
> I need to zoom out an astronomical image, in order to make it visible a
> part of the sky which is NOT included in the image itself. In other
> words, I need to display the original image in a smaller region of the
> picture and the rest is black. BUT, I need to preserve the RA and DEC
> coordinates in the black part of the picture, because I have to draw a
> box at certain coordinates to show that it is well outside the original
> image. Moreover, I need to put RA and DEC axis (as it's done with
> imcontour), BUT for all the total picture, not only the original image.
> I hope it's clear! In any case, I've done it succesfully with ds9, so
> that I can show what I want to you, but in IDL the result can be much
> better!
There are a number of routines in the Goddard idlastro library for
manipulating images and their FITS astrometry headers at the same time.
In particular, you can use HREBIN for resizing (zooming out). Then you can
use imcontour for the axes labels - just set /noerase and /nodata when
calling it.
- Marshall
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| Re: Zoom out of astronomical image preserving header info [message #42686 is a reply to message #42611] |
Fri, 18 February 2005 03:19  |
burkina
Messages: 32
Registered: February 2005
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Member |
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Thank you Marshall for your reply.
The problem with hrebin (and hcongrid) is that they don't zoom the
image out as I need (like atv for example). They will produce an image
with that number of pixels, so that if the zoom factor is 2, an
original image of, say, 300x300, will become 600x600. This means a lot
of time in processing the image when you need a very large zoom factor
(as in my case) and enormous image files. That's not what I need. I
actually need a costant image size, but with the original image
shrinked to the desired dimension.
In practice, I need a functionality completely equivalent to the ATV
zoom, together with the possibility to re-center the final image where
I want. I need space outside the image with the correct RA and DEC
coordinates. ATV does it, but it can't do other things I need. That's
why I can't use it directly.
I'm sure it's easy....
Stefano
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