Re: Emacs Survey: Toolbars

[Tomas Hlavaty]

On Fri 25 Dec 2020 at 12:20, Stefan Monnier <monnier@iro.umontreal.ca> wrote:
>> It is trivial for monochromatic documents.
>
> Actually, not even: if you've ever looked at the "negatives" used for
> analog black&white photos you'll surely understand that inverse-video
> doesn't work so well for images (mostly because it inverses lights and
> shadows, thus confusing the semantics).

Ok, I did not mean gray-scale.  I meant text in black ink on white paper
WYSIWYG edited in Emacs with reverse video colors.  I cannot recall the
proper name for it at the moment but you get the idea.

Now add third color, e.g. to highlight a word in the document.  Simply
swapping background and foreground color can make the highlighted word
badly readable, if the color stays the same.

> For a "pure" text or other such circumstances where the colors don't
> carry much meaning, it's not too hard to do something like "inverse
> video" with an acceptable result, but for photos or comparable kinds
> of images, I suspect that it's somewhere between very hard and
> impossible.

We can leave photos and images out of the question and simply preserve
their colors.

Do you have suggestion for automatically computing "it's not too hard"
color mapping for "inverse video" "pure" text?