[AstroPy] Some Feedbacks about Astropy
Stuart Mumford
stuart at mumford.me.uk
Thu Jul 3 12:27:01 EDT 2014
hello,
Just a quick reminder about the feature identification and tracking
algorithms (as well as RANSAC) that were implemented in scikit-image last
summer. http://scikit-image.org/docs/0.10.x/api/skimage.feature.html
So if anyone is going to work on registration they are probably a very
helpful source of code and advice. SunPy has a cross correlation
registration routine that uses scikit-image's match_template function.
Stuart
On 3 July 2014 15:47, Martin Beroiz <martinberoiz at gmail.com> wrote:
> Hello,
>
> I also did my own registration code based on an approximate rotation +
> translation and source correspondence with a RANSAC
> algorithm. It’s inspired in openCV’s algorithms for image registration and
> it works with stellar fields like the ones I use.
> (openCV methods didn’t work out of the box for the images I needed)
>
> But I would like to see something like astrometry.net does, identifying
> pentagons or other polygons in both images.
> In fact I tried to do something like that myself and then I set that aside
> for lack of time.
> Does anyone know if there’s anything like that implemented yet? I would
> like to see that included in astropy.
>
> M.
>
> On Jul 3, 2014, at 2:18 AM, Adam Ginsburg <adam.g.ginsburg at gmail.com>
> wrote:
>
> I agree with Tom's points, but I'd also like to clarify that the
> variety of replies were not all to the same question.
>
> The scipy.map_coordinates+astropy.wcs, pyAST, and montage utilities
> that I, Ray, and Sophie mentioned solve the problem of image
> regridding and reprojection, which as Tom points out belongs in
> astropy-core eventually.
>
> The montage approach uses a wrapper to an underlying C program called
> montage that needs to be installed independently. The scipy approach
> is more purely python, but it requires interpolation and is not flux
> conserving (montage is). The pyAST approach wraps another underlying
> C library and implements its own resampling that can be flux
> conserving depending on certain flags chosen (but Dave Berry, correct
> me if I've gotten something wrong here):
> http://dsberry.github.io/starlink/node1.html#Resample
> http://www.starlink.rl.ac.uk/docs/sun210.htx/node371.html
> These routines could probably live in something called
> astropy.reprojection or something similar.
>
>
>
> The second class of problems addressed is image registration, which I
> think is being treated in ccdproc, SRPAstro, and the methods that Ray
> mentioned. I think these are each niche codes with a different role;
> image registration based on star matching is very different from that
> based on FFTs and extended emission matching. For a summary of the
> codes available for extended emission registration, have a look at
>
> http://image-registration.readthedocs.org/en/latest/#programs-implementing-these-methods-in-various-languages
> .
>
> I hope this is useful clarification, but please correct me if I
> misrepresented anyone's code here.
>
> On Thu, Jul 3, 2014 at 8:10 AM, Thomas Robitaille
> <thomas.robitaille at gmail.com> wrote:
>
> Paul Kuin wrote:
>
> Reading all this, I think that part of the success of the IDL Astro
> library is due to having one head, Wayne Landsman, put it all together.
> This reads like a conversation on the tower of Babel. Everyone their own
> method. Someone should take the time to check and compare all the
> different implementations. Some funding for such work would be very
> useful and save on duplication. I think this is a task that the IAU
> could(should?) be involved in.
>
>
> Reducing duplication is precisely the goal of the Astropy project - in
> fact, we have a rule that 'affiliated' packages should not duplicate
> functionality from the core, and also avoid duplication amongst one
> another. See the original vision document:
>
> http://docs.astropy.org/en/stable/development/vision.html
>
> If you are interested in getting involved, you can join the astropy-dev
> mailing list. As part of the Astropy project, there have already been a
> number of successes in merging existing packages to provide a core
> implementation (for example the cosmology routines).
>
> On the more specific topic of re-projection - this is clearly a highly
> requested feature, and I think it should be targeted as something that
> should have an implementation in the core astropy package that then gets
> used by all other packages.
>
> As a side note, the fact there was more than one reply to the original
> question is a testimony to the strength of the development community in
> Python - people are clearly not just waiting for one person to just
> write it all. Yes, we need to all make an effort to not duplicate things
> needlessly, but on the other hand, having two different ways of
> approaching the same problem is not always bad.
>
> Cheers,
> Tom
>
> Paul
>
>
> On Wed, Jul 2, 2014 at 6:15 AM, Guang Yang <yg1991 at mail.ustc.edu.cn
> <mailto:yg1991 at mail.ustc.edu.cn>> wrote:
>
> Thank all of you for giving those advices. I think I won't bother to
> switch between python and IDL in my next project. ^^
>
> Best wishes,
> Guang
>
>
> -----Original email-----
> *From:* "Sofia Lianou" <slianou at uwo.ca <mailto:slianou at uwo.ca>>
> *Sent Time:* Jul 2, 2014 5:14:53 AM
> *To:* "Astronomical Python mailing list" <astropy at scipy.org
> <mailto:astropy at scipy.org>>, "Adam Ginsburg"
> <adam.g.ginsburg at gmail.com <mailto:adam.g.ginsburg at gmail.com>>
> *Cc:* "Pauline Barmby" <pbarmby at uwo.ca <mailto:pbarmby at uwo.ca>>
>
> *Subject:* Re: [AstroPy] Some Feedbacks about Astropy
>
> Hello,
>
> This is something that imagecube is doing, too, and the package
> is hosted here:
> http://sophiathl.github.io/imagecube/
>
> Beta release to follow soon, along with proper documentation.
>
> Cheers,
> Sophia, Pauline, and Jeff
>
> On 07/01/14, *Adam Ginsburg * <adam.g.ginsburg at gmail.com
> <mailto:adam.g.ginsburg at gmail.com>> wrote:
>
> 1. I find no tools to align two images, i.e. to uniform
>
> their astrometry, pixel scale, image size and etc.
> hastrom.pro <http://hastrom.pro>
> (http://idlastro.gsfc.nasa.gov/ftp/pro/astrom/hastrom.pro) is
> a good example to perform such a task.
>
> I've written a tool to do that:
>
> https://github.com/keflavich/FITS_tools/blob/master/FITS_tools/hcongrid.py
> ...I think it does what hastrom does, not hcongrid, which means I
> should change the name.
>
> Otherwise, you can use the montage wrapper:
> http://www.astropy.org/montage-wrapper/
>
>
> --
> Adam Ginsburg
> Fellow, European Southern Observatory
> http://www.adamgginsburg.com/
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> --
>
> * * * * * * * * http://www.mssl.ucl.ac.uk/~npmk/ * * * *
> Dr. N.P.M. Kuin (n.kuin at ucl.ac.uk <mailto:n.kuin at ucl.ac.uk>)
> phone +44-(0)1483 (prefix) -204927 (work)
> mobile +44(0)7806985366 skype ID: npkuin
> Mullard Space Science Laboratory – University College London –
> Holmbury St Mary – Dorking – Surrey RH5 6NT– U.K.
>
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> --
> Adam Ginsburg
> Fellow, European Southern Observatory
> http://www.adamgginsburg.com/
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