Image process in gdk

["Luis Ramirez" <luisramirez22 gmail com>]

Hello

I am just a beginner in gtk and after working with the excellent samples
available I wanted to begin with a simple program that loads an image and
applies different processes on it (brightness, B&W, rotate, ...).
If I load and process the image before gtk_main() everything goes right but
if I link the call_back of a Button to a function, the image does not
change.
I have tried to use the widget expose_event but it works with a widget
created with gtk_drawing_area_new(), but not with a widget created with
gdk_pixbuf_new_from_file().
Do you have any simple example about it?. It is simpler to show images with
cairo?

Luis