I’d like to know how with the help of python, how i could manipulate pixels, in compositor.
So having a final rendered image, then launch my script and edit pixels into a new image result.
I’ve got some ideas of a new kind of filter, i could code it in c#, but rather make something that anyone could use later.
So maybe later it could becomme an addon if the filter worksout fine.
Maybe
is the image module isnt part of the default blender install 
Well no but it isn’t difficult to add it to your scripts folder 
Python doesn’t support image manipulation out of the box. If you’re planning to release this you could bundle it with an install script although you would have to know what operating system the user is on first, and the user would need to have write permissions to that directory - it’s better to make this an ‘addon’ in my opinion that covers all eventualities.