[gnuastro-devel] [task #14574] Crop by center options standard agnostic

[Mohammad Akhlaghi]

URL:
  <http://savannah.gnu.org/task/?14574>

                 Summary: Crop by center options standard agnostic
                 Project: GNU Astronomy Utilities
            Submitted by: makhlaghi
            Submitted on: Tue 27 Jun 2017 11:32:40 PM CEST
         Should Start On: Tue 27 Jun 2017 12:00:00 AM CEST
   Should be Finished on: Tue 27 Jun 2017 12:00:00 AM CEST
                Category: Crop
                Priority: 5 - Normal
              Item Group: Enhancement
                  Status: In Progress
                 Privacy: Public
        Percent Complete: 90%
             Assigned to: makhlaghi
             Open/Closed: Open
         Discussion Lock: Any
                  Effort: 0.00

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Details:

Currently, if you want to crop a region around the pixel (A,B) in an image
with crop, you have to use `--xc=A --yc=B'. On the other hand, if you want a
crop around the RA and Dec of (R,D), you have to use `--ra=R --dec=D'. Each
standard also has its own separate option to specify the width: `--iwidth' and
`--wwidth'. In parallel, Crop also has the `--mode' option to specify the
coordinate standard (for cases like `--polygon', where only one option is used
for both standards).

This can all be confusing, just adds to the number of options (makes things
harder for the user) and also makes maintaining Crop harder. The main reason
for this is historical: Crop is Gnuastro's first program, so I wasn't too
experience and all these options grew very gradually.

So I am now working on a correction where a single `--center' and `--width'
option can be used to identify the center and width of the crop. They both
accept multiple values (separated by a comma) and can also accept fractions.
So now, the crops defined by their center can be rectangular too, not just a
square. With this change, the role of the `--mode' option becomes more
prominent because it is the sole way to identify the nature of the values
given to this option.




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