[gnuastro-devel] [task #14980] Max-trees to grow true clumps

[Mohammad Akhlaghi]

URL:
  <http://savannah.gnu.org/task/?14980>

                 Summary: Max-trees to grow true clumps
                 Project: GNU Astronomy Utilities
            Submitted by: makhlaghi
            Submitted on: Fri 06 Jul 2018 01:32:15 PM CEST
         Should Start On: Fri 06 Jul 2018 12:00:00 AM CEST
   Should be Finished on: Fri 06 Jul 2018 12:00:00 AM CEST
                Category: Segment
                Priority: 5 - Normal
              Item Group: Enhancement
                  Status: Postponed
                 Privacy: Public
        Percent Complete: 0%
             Assigned to: None
             Open/Closed: Open
         Discussion Lock: Any
                  Effort: 0.00

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Details:

In Segment, after true clumps are found, they are "grown" simply by sorted
pixels (as you see in Figure 10
<http://iopscience.iop.org/article/10.1088/0067-0049/220/1/1/meta#apjs512983f10>
of the NoiseChisel paper). 

This is only a very crude first approximation to identifying "objects" over
the detection and has many problems. For example, an "object" associated with
a small peak can easily cover a very large area of a large galaxy's diffuse
underlying flux for example.

A better way to grow the true peaks/clumps over NoiseChisel's detected
(non-background) pixels may be to use "Max-tree"s like what is used in
MTObjects
<https://www.degruyter.com/view/j/mathm.2016.1.issue-1/mathm-2016-0006/mathm-2016-0006.xml>.


>From the example images in that paper (for example Figures 7, 8, 12 and 13),
you see that because of this higher-level structure, the smaller peaks over a
large extended region are much more accurately separated from the diffuse flux
of the background and they don't block it (like they do in segment currently,
which is not good). 

A simple visual inspection thus suggests that this is probably a much better
way to grow the true clumps which is worth testing (and hopefully
implementing) in Segment. 

I will try to do this after I find some free time (my current project
finishes), but if anyone is interested until then, you can start it already,
and I would be happy to help ;-)...




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