Re: [Gimp-user] Image luminosity

[Ofnuts <ofnuts gmx com>]

On 03/07/18 15:10, WMusc wrote:
> > Something like:
> >
> > Color>Desaturate (luminosity) and check the average or median in the
> > Histogram dialog.
> Thanks for the tip. Do you know whether that approach provides the mean (median,
> etc.) luminosity value before or after desaturation? It looks to apply the
> effect so it's unclear to me. If the program applies it uniformly across all
> images I may be able to use it as a proxy for luminosity but would like to avoid
> that if possible.
I expect Color>Desaturate>Luminosity to not change the luminosity of the 
pixel. The grey value after is normally the luminosity you would have 
computed from the RGB components you have in the initial image.

This said, in 2018 I'm surprised you are engaging in such manual labor. 
Find someone (intern?) to write a small program that will extract all 
these data directly from the image files and create a spreadsheet with 
the results.