hello, some months ago I saw a black and white drawing on twitter
of a young man watching the moon in the stary night sky
with a telescope on a tripoid.

when you clicked the picture of the single tweet to get the right size
on the computer internet page (not on mobile)
some areas of the white changed to black ... i don#t find it in the moment
(or vice versa. black to white)

when i opened it with gimp i remember that the very extrem values
in the colour measure inspector (dunno the english expression)
were very high - so recently i opened a normal RGB pic and saw there
are quite some differences with the curves and values - but in general
the difference is not that big (pic of timeline vs. pic of single tweet and click on it)
to suppress the whole specific color value - or how should i say?

so how can i aim for that trick when producing a pic???

i mean searching for this matter just with gimp curves and measures of
the pic's colours gave me some amazing discoveries of the work with it's discipline.

i still did not find that tweet -
but i want to add that it is aswell
quite informative to play a little with the curves dialog
having opened this e.g. 900gradients_for_GIMP_Inkscape_by_nevit

ps: it's this dialog - that would be a mac

I have that pack. I never did look at all of them but I did save out some of the nice pinks.

thank you molly for the reply - yes, this is a great palette -
(not sure if I even found it in this forum..)

now I found my guy with telescope after having more google
and the resulting title of the page is "Twitter Hack for Rollover Images"

the feature "searching google with an image instead of text" is very helpful

Here's a good overview, Twitter Image That Changes When Clicked.

thank you mod. that is a good link.
sorry for my bad memories - i guess i was quite wrong with them
and mixed the things with black/white and RGB and values.
in the moment it's so much that i need a break now