IronPython and PythonNet have access to the .Net framework (a huge .Net library) so here is an alternative you can use
import sys
import clr
import System
clr.AddReference('ProtoGeometry')
from Autodesk.DesignScript.Geometry import *
clr.AddReference('System.Drawing')
from System.Drawing import *
from System.Drawing.Drawing2D import *
myBitmapPath = IN[0]
out_folder = System.IO.Path.GetDirectoryName(myBitmapPath)
out_bmp_path = out_folder + "\\out_img.png"
text_to_draw = IN[1]
bmp = Bitmap(myBitmapPath)
rectf = RectangleF(bmp.Size.Width / 2, bmp.Size.Height / 2 - 180, 160, 30)
g = Graphics.FromImage(bmp)
g.SmoothingMode = SmoothingMode.AntiAlias;
g.InterpolationMode = InterpolationMode.HighQualityBicubic
g.PixelOffsetMode = PixelOffsetMode.HighQuality
g.DrawString(text_to_draw, Font("Tahoma", 20), Brushes.Black, rectf)
g.Flush()
bmp.Save(out_bmp_path)
OUT = bmp