On 03/10/2018 03:55 AM, Ofnuts wrote:
On 03/07/18 15:10, WMusc wrote:
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.
Thanks for the tip. Do you know whether that approach provides the
etc.) luminosity value before or after desaturation? It looks to apply
effect so it's unclear to me. If the program applies it uniformly
images I may be able to use it as a proxy for luminosity but would
like to avoid
Color>Desaturate (luminosity) and check the average or median in the
that if possible.
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
Before finding an intern to write a program, it might be a good idea to
figure out whether the metrics you've decided to extract are actually
useful to the task at hand. Garbage in/garbage out, as I've been trying
to say over in the pixls.us thread on this topic:
As far as extracting information from an image, ImageMagick might be a
better choice than GIMP - more available metrics, though again it's an
open question as to whether any of the metrics actually help you decide
whether an image is "too this" or "not enough that". Remember the red
square in the middle of an otherwise solid gray image that I posted to
the pixls.us thread - the relative luminance of the red square is
exactly the same as the relative luminance of the background, but I'm
fairly sure just about everyone will say the red square is "brighter",
as indeed it according to the definition of "brightness" used in current
color appearance models.
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