[gnuastro-devel] [task #14313] Change definition of rectangular section cropping limits to be inclusive

[Mohammad Akhlaghi]

URL:
  <http://savannah.gnu.org/task/?14313>

                 Summary: Change definition of rectangular section cropping
limits to be inclusive
                 Project: GNU Astronomy Utilities
            Submitted by: leeskelvin
            Submitted on: Fri 20 Jan 2017 08:30:42 AM JST
                Category: None
                Priority: 5 - Normal
                Severity: 1 - Wish
              Item Group: None
                  Status: None
                 Privacy: Public
             Assigned to: None
        Originator Email: 
             Open/Closed: Open
         Discussion Lock: Any
        Operating System: None

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Details:

When defining a rectangular section to crop from a larger image using the
--section argument of ImageCrop, I believe it would make more sense for all
coordinates in X1:X2,Y1:Y2 to be inclusive.

For example, if I wish to cut out a square region in the lower-left corner of
a FITS image of size 3x3, the principle of least surprise would lead me to
believe that this command should be: 

astimgcrop --section=1:3,1:3 input.fits

However, the current definition of cropping coordinates within ImageCrop is
inclusive for the lower-left corner (X1 and Y1) yet exclusive for the
upper-right corner (X2 and Y2). The above command should therefore leave me
with only a 2x2 FITS image as an output. Logically, this does not seem to
follow.

Furthermore, many other contemporary astronomy image cutting software already
adopts inclusive coordinates at both extremes, for example, NASA HEASARC's
'fitscopy' and STScI's 'imcopy'. Many astronomers already familiar with these
software may not appreciate that ImageCrop has adopted an alternative
definition.





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