[gnuastro-devel] [task #14318] ImgCrop does not create the output image when the center is blank

[Mohammad Akhlaghi]

Follow-up Comment #5, task #14318 (project gnuastro):

Thanks, yes this is the expected behavior: when you use the `--section'
option, you have not defined the crop by its center, so it makes no sense to
check the center of the crop (you might have done this to do some other thing
in this region, e.g., add profiles/images and etc). 

So even when you give a value to the `--checkcenter' (`-c') option, no center
checking is done when the crop is not defined by its center.

As an alternative you can see the effect of checking the center with this
command (in the `tests/' directory):


$ ../bin/imgcrop/astimgcrop --xc=25 --yc=25 --iwidth=51 --checkcenter=3
mkprofcat1.fits
ImageCrop started on Sun Jan 22 15:56:30 2017
  - Read metadata of 1 image.                     0.000624 seconds
  ---- mkprofcat1_cropped.fits        not created (blank center) from 1
input.
ImageCrop finished in:  0.012872 seconds


If you remove the `--checkcenter=3' option, then the exact same (fully NaN)
image will be created as the one your command built:


$ ../bin/imgcrop/astimgcrop --xc=25 --yc=25 --iwidth=51 mkprofcat1.fits
$ astheader mkprofcat1_cropped.fits | grep ICF
ICF1_1  = 'mkprofcat1.fits'
ICF1PIX = '1:50,1:50'          / Range of pixels used for this output.


Could you have a look a the new "ImageCrop modes" section of the book (it has
been fully re-written):


$ info gnuastro "ImageCrop modes"


After reading this, the new behavior should become more understandable, so
your comments (on making it better/more-clear or resolving other issues) on it
would be really great.

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