chg in add_shift
This is only doing the high pass and lo pass or rows.  It appears that the image below in the middle on the top is lo pass and image on lower half is the high pass.

Using the PIL cropped image with the following steps.
im1=im.crop((0,0,256,128))

im2 = im1.resize((128,128))

im2.save("fwt1.png")