This trims Anilist portraits by n pixels on all sides (default 2).

trim-anilist-portraits.py

from PIL import Image
import glob, os, sys

'''
Place images in the "Input" folder for trimming.
Results of trimming will be created in the "Output" folder.
Input and Output folders will be automatically created if they don't exist.

Add a number as an argument to change how many pixels to crop (default 2).
'''

def trim(im, n):
	w, h = im.size # Width and height of image
	return im.crop((n, n, w-n, h-n)) # Crops top-left and bottom-left coordinates by n pixels

# Checks if Input and Output folders exist.
# There's probably a prettier way of doing this.
if not os.path.exists("Input"):
	os.makedirs("Input")
	print("Folders created. Place images in the Input folder for trimming.")
if not os.path.exists("Output"):
	os.makedirs("Output")

# Sets pixels to crop by user argument. If none exists, use default 2.
try:
	pixels = int(sys.argv[1])
except:
	pixels = 2

# Initialises list containing images. Order doesn't matter.
folder = glob.glob("Input\*.jpg") 
folder += glob.glob("Input\*.png")

num = 0
for i in folder:
	# Goes through each image in folder and trims it.
	# Saves results to Output folder. Original file name is retained.
	num+=1
	im = Image.open(i)
	im = trim(im, pixels)
	f = i[-3:] # Format of image. Not compatible for file types larger than 3 chars
	filename = i[6:-4]
	if f == "jpg":
		im.save("Output/%s.jpg" % filename, "JPEG", quality=95, optimize=True, progressive=True)
	elif f == "png":
		im.save("Output/%s.png" % filename, "PNG", optimize=True)
	else:
		print("Unknown image format. Only PNG and JPEG files are compatible.")

Doesn't work for .png files yet. Will fix later.
Fixed.