gdk_drawable_get_image not available in GDraw.drawable

Hello,

I want to use the gdk_drawable_get_image function as included in:

https://developer.gnome.org/gdk2/2.24/gdk2-Drawing-Primitives.html

Most of the drawing primitives in this page are available in the
GDraw.drawable class:

http://lablgtk.forge.ocamlcore.org/refdoc/GDraw.drawable-c.html

However, gdk_drawable_get_image (and gdk_drawable_copy_to_image)
appears to be missing.  Can I use it?  Or it is not supported because
it is deprecated perhaps?  The above page says:

> gdk_drawable_get_image has been deprecated since version 2.22 and
> should not be used in newly-written code.
> Use drawable as the source and draw to a Cairo image surface if you
> want to download contents to the client.

I want to draw various objects (images, lines, rectangles, etc.) using
GnoCanvas and then convert the resulting image to an array of colors
for manipulation.  Should I investigate what Cairo is?  Any
information appreciated.  Thank you in advance.

Sincerely,

-- 
Kenichi Asai