Re: highlighting chars on a path

[Mojca Miklavec <mojca.miklavec.lists@gmail.com>]

On Sun, Oct 18, 2009 at 21:11, Aurelien Giraud wrote:
> Hello,
>
> I am new to ConTeXt and I have looked on the internet for a way to do
> something special. Unfortunately I have not found any solution.
>
> I hope this is the right place for such a question. I apologise otherwise.
>
> I would like to highlight (e.g. put in bold, or change the color...) any
> character on a page which sits on a chosen path. I would like to be able to
> position for instance an invisible circle on a page and have all the
> characters "in contact" with this circle change color so that the circle
> become visible via these characters. Is it something I could do with
> ConTeXt?

This won't be of any help to you ...
... but I remember seeing one of early luatex showcases with
characters colored in the shape of circular wave (smoothly varying
color - really impressive), but I have no idea if that has ever been
published anywhere. (I'm writing this because I'm also interested to
see that masterpiece again.)

Mojca


I don't know how to do it, but I would bet that it is possible to
misuse luatex for it (before printing out a character you check its
position on page, do some basic math and output the desired color).
It's usually done by overwriting some lua function. Just a tiny
warning if you do get a solution from someone: LuaTeX might not be
absolutely stable in this respect yet, so you need to take in account
some slight possibility that the low level interface undergoes some
changes in future. In that case you might need to adapt your code
after a while. You should not worry about it now, it's just good to
keep it in mind.
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