PixbufDestroyNotify

A function of this type is responsible for freeing the pixel array of a pixbuf.

The gdk_pixbuf_new_from_data() function lets you pass in a pre-allocated pixel array so that a pixbuf can be created from it; in this case you will need to pass in a function of type GdkPixbufDestroyNotify so that the pixel data can be freed when the pixbuf is finalized.