Basic image manipulation

[Goran =?utf-8?q?Raki=C4=87?= <gox devbase net>]

I have a program where user needs to select an image (in JPEG or GIF format) 
and I need to store it in database. I can read it from selected file, and 
show it as GtkImage with GdkPixbuf in application, but...

I need to verify if image type is JPEG or GIF and than to resize it to 200px 
width. Can Gtk&Gdk do that, or I need to use something other like GD library?

How can I than display that image data from database (SQLite) in GtkImage?

I am very novice in this area of programming so every hint will be good.

Bye,
Goran