DOC: Conversion guide from pyregion

[pllim]

As suggested by @prajwel in astropy/pyregion#161 (comment)

I knew this was just a matter of time. Pyregion is part of many packages due to its age. Perhaps we can create easy porting guidelines for people wanting to port their code to Regions 🤔?

[neutrinoceros]

Sorry if this isn't the right place to ask, but are there any equivalent to pyregion.open and pyregion.parse in regions per chance ?

[larrybradley]

I think you are looking for Regions.read and Regions.parse. Examples here: https://astropy-regions.readthedocs.io/en/stable/region_io.html

[prajwel]

I think the following comparisson could be useful.

Pyregion

contours = pyregion.open('contours.reg').as_imagecoord(wcs.to_header())
patch_list, artist_list = contours.get_mpl_patches_texts()
    
for p in patch_list:
    ax.add_patch(p)
for t in artist_list:
    ax.add_artist(t)

Regions

contours = Regions.read('contours.reg', format='ds9')    
for sky_region in contours:
    pixel_region = sky_region.to_pixel(wcs)
    _ = pixel_region.plot(ax=ax)