create thumbails for all JPG files in a folder as 128 128 JPEG files

make_thumbs.py

import os, sys
import PythonMagick
from os.path import expanduser
import glob
import time
directory = expanduser('~\\pictures\\clarifai\\')
thumbsdirectory = expanduser('~\\pictures\\clarifai\\thumbs\\')
thumbs=glob.glob1(thumbsdirectory, "*.THUMB.JP?")
jpgs=glob.glob1(directory, "*.JPG")
thumbs = [suffix.replace('.THUMB.JPEG', '.JPG') for suffix in thumbs]
pictures = list(set(jpgs)^set(thumbs))

def Resize(image, w, h):
    img = PythonMagick.Image(image) # copy
    s = "!%sx%s" % (w, h)
    img.resize(s)
    return img

def Paste(destImage, sourceImage, x1, y1):
    op = PythonMagick.CompositeOperator.OverCompositeOp
    # a kluge to prevent changing to grayscale - doesn't always happen
    type = destImage.type
    destImage.composite(sourceImage, x1, y1, op)
    destImage.type = type
    return destImage

logo = PythonMagick.Image(directory+"overlay\\watermark.png") # make a copy of the watermark overlay - supports transparency

for infile in pictures:
    outfile =    os.path.splitext(infile)[0] + ".THUMB.JPG"
    time.sleep(.1)
    try:
        progress="Before Open"
        im = PythonMagick.Image(directory+infile) # make a copy
        
        progress="After Open"
        im = Resize(im, 128, 128)
        im = Paste(im, logo, 0, 0)
        #im.unsharpmask(.7,0.2,0.4,0.008) # unsharpmask(radius,sigma,amount,threshold)
        im.write(thumbsdirectory+outfile)
        progress="Complete"
    except IOError:
        print ("cannot create thumbnail for", directory+infile, thumbsdirectory+outfile, progress)

This expects ANOTHER file to be in directory+"overlay\watermark.png" that will be melded over the JPG.
use transparency.

Don't want to use ImageMagick?
You could use python directly but YMMV
http://stackoverflow.com/questions/22558976/oserror-decoder-jpeg-not-available-on-windows