  We provide line luminosities and spectroscopic templates of prominent optical
emission lines of 133 Galactic Wolf-Rayet stars by exploiting Gaia DR3
parallaxes and optical spectrophotometry, and provide comparisons with 112
counterparts in the Magellanic Clouds. Average line luminosities of the broad
blue (He II 4686, C III 4647,51, N III 4634,41, N V 4603,20) and yellow (C IV
5801,12) emission features for WN, WN/C, WC and WO stars have application in
characterising the Wolf-Rayet populations of star-forming regions of distant,
unresolved galaxies. Early-type WN stars reveal lower line luminosities in more
metal poor environments, but the situation is less clear for late-type WN
stars. LMC WC4-5 line luminosities are higher than their Milky Way
counterparts, with line luminosities of Magellanic Cloud WO stars higher than
Galactic stars. We highlight other prominent optical emission lines, N IV
3478,85 for WN and WN/C stars, O IV 3403,13 for WC and WO stars and O VI
3811,34 for WO stars. We apply our calibrations to representative metal-poor
and metal-rich WR galaxies, IC 4870 and NGC 3049, respectively, with spectral
templates also applied based on a realistic mix of subtypes. Finally, the
global blue and C IV 5801,12 line luminosities of the Large (Small) Magellanic
Clouds are 2.6e38 erg/s (9e36 erg/s) and 8.8e37 erg/s (4e36 erg/s),
respectively, with the cumulative WR line luminosity of the Milky Way estimated
to be an order of magnitude higher than the LMC.
