drawing on an image, colour manipulation

["Johan Aberg" <abergster gmail com>]

Hello!
I'd like to draw a simple rectangle over a Gtk2::Image. What would be
the best way of doing this. There are a few options, canvas, drawable,
composit etc.

Ideally, this rectangle would trace position of the mouse in realtime.

Also, are there any built in colour corrections, such as brightness or
multiply RGB values of an pixbuffer?

I've been trying to convert back and forth between imagemagicks
ImageToBlob/BlobToImage to manipulate the colours. Any better ways of
doing it?

Any ideas?

Cheers