Something

def python_resize(fname, startXY, scaleXY):
	dname = os.path.dirname(fname)
	files = glob.glob(os.path.join(dname, '*'))
	i = startXY
	for f in files:
		#name, ext =  os.path.splitext(f)
		dname, name = os.path.split(f)
		newfilename = os.path.join(dname, "resized"+name)
		print "Scale ",name,"save to",newfilename
		image = pdb.gimp_file_load(f,f)
		#drawable = pdb.gimp_image_get_active_drawable(image)
		nh  = int(round(image.height * i))
		nw = int(round(image.width * i))
		print i, nh, nw
        # resize the image to the containing box
		pdb.gimp_image_resize(image, nw, nh, 0, 0)		
		# save and close the file
		if len(image.layers) > 1:
			finalLayer = pdb.gimp_image_merge_visible_layers(image, CLIP_TO_IMAGE)
		else:
			finalLayer = image.layers[0]
		pdb.gimp_file_save(image, finalLayer, newfilename, newfilename)
		i *= scaleXY