code: func CreateImageSurface(format Format, width, height int) *Surface {
  	c := C.cairo_image_surface_create(C.cairo_format_t(format),
  		C.int(width), C.int(height))
  	s := wrapSurface(c)
  	runtime.SetFinalizer(s, (*Surface).destroy)
  	return s
  }
docs: // CreateImageSurface is a wrapper around cairo_image_surface_create().