How can I update the gdk-pixbuf raw data?

[zzojaji aim com]

Hello,  

  I am new to GTK and have a problem with gdk-pixbuf, How can I update the pixbuf raw data?  

  There is a pixbuf constructed from an image file, I  want to change raw data behind it and upload new data 
back to pixbuf. I  am using the "gdk_pIxbuf_save_to_buffer" for accessing raw data, but I  don't know how to 
upload the buffer back to the pixbuf!  

  Thanks, in advance,  

  Zahra Zojaji