Hello if i trace over a picture in order to make another picture, example, if i trace over this picture rule34.xxx/index.php?page=post&s=view&id=1705621
In order to edit her to another character, will people see me like thief or not? ( in my opinion, i consider that as a robbery, but i want other opinion )
If not, will i be allowed to post it on this site or any other 18+ such as xhamster, ... ?

It depends. I see no harm in imitating the pose, proportions, etc. if the overall image is different enough compared to the original. It wouldn't really be considered an edit or plagiarism unless it looks too similar.

If someone looked at the trace and almost immediately thinks "Hey, that looks just like..." then you've done it wrong, unless it's a parody or something. There are a few of those lying around.

Technically no you will only be stealing the composition which is not a robbery so long as you change the character more than just color. Artists have traced other artists for years. I can honestly say i have traced a few designs myself for my personal projects.

Thanks for the reply.

It would only be a robbery if you threatened the artist with violence. Robbery and theft are not synonymous.

It wouldn't even be theft (technically, you're not taking anything) so the worst you can be accused of is plagiarism (copying someone else's work and calling it your own) which would only happen if the new image is too similar to the original. As long as they're different enough, you're fine.

Don't trace! Learn how to draw. :|