This code was used to make simulation counterparts to observation HEALPIX maps from Planck, ROSAT, and SDSS. It works with a rectangular map of a scalar quantity (tSZ signal, X-ray counts, galaxy number) and projects them onto a spherical HEALPIX map. This map can then be used as an input into a cross-correlation code such as NaMASTER.
Some examples of the resulting maps:
More information can be found in my paper: https://arxiv.org/pdf/1907.06645.pdf