When setting the intercept to zero (which is irrealistic, but can be useful), @varzakis and I see segfaults when the detector is "inside" the image (e.g. for small detector radius). The calc_psf_bin code doesn't seem to handle the case of a very narrow (or zero width) PSF. Relevant code:

(di could be very large/infinite)

(i1 would be undefined but was in our case a very negative number, Ncb should then be 0, but isn't necessarily)

crashes as i1 is out-of-range

I think this needs 2 modifications:

• if psref is very small, just set

  psf->val[0] = 1.F;`
  psf->ind[0] = jm;
  psf->Nib = 1;

• add an assert that i1>=0

@varzakis @danieldeidda ok?