Zoom-in line-ratio maps of three example H II regions (IDs 112, 113 and 120 from bottom to top). From left to right: Maps of Hα flux, S III/S II, O III/S II, and O III/Hβ ratios. In panel a, the blue crosses are the geometrical centroids of the nebular mask, the magenta circles, and the green triangles indicate the peaks of the Hα and O III emission within the nebular mask, respectively. The dashed green apertures have a radius of 5 and 10″, respectively. In panel d, green and orange stars indicate massive stars (Sect. B.1) and WR stars (Sect. B.2), respectively.