[pygtk] How can I do to know the value of a pixel in a pixmap ?

[=?iso-8859-1?Q?Val=E9ry?= Febvre]

Hello,

I'am new and I need help.
I have a drawing area and I create a pixmap in the drawing area

da = GtkDrawingArea()
pixmap = create_pixmap(da.get_window(), da.width, da.height, -1)

and after, I draw lines, rectangles, points, ... in the pixmap

How can I do to know the value of a pixel in the pixmap ?

Thanx in advance
Cheers
Valery