ReadPixel() and WritePixel() functions for sf::RenderWindow

[zeocyte]

I think that we should really implement this feature on SFML's graphics.

Please note that there's lots of useful things that these functions can do like rendering stars, graphical effects, dotted lines, etc.

And its just simple to implement (glReadPixels() perhaps).

[Laurent]

This is a very bad and outdated approach, graphics cards are made for rendering primitives, not writing pixels directly the back buffer.

The new graphics API in SFML 2 allows to render points and lines, and for effects, you can use shaders.