transfer_png_sprite_offsets.py

import sys, os, png

usage = "Transfers ZDoom/SLADE-format grAb chunk from donor to target PNGs.\n"\
        "Usage:\n\tpython.exe transfer_png_sprite_offsets.py donor target\n\n"\
        "Donor and target can either both be filenames or directories.\n"\
        "Subdirectories are not included."

def do_the_thing(dnr_path, tgt_path):
    dnr_png = png.Reader(filename=dnr_path)
    tgt_png = png.Reader(filename=tgt_path)
    dnr_chunks = list(dnr_png.chunks())
    tgt_chunks = list(tgt_png.chunks())
    if dnr_chunks[1][0] == b'grAb':
        if tgt_chunks[1][0] != b'grAb':
            tgt_chunks.insert(1,dnr_chunks[1])
            with open(tgt_path, 'wb') as output:
                png.write_chunks(output, tgt_chunks)
        else:
            print("\nTarget already has offsets: " + name)
    else:
        input("\nNo donor offset chunk found: " + name)

if len(sys.argv) != 3:
    input(usage)
    sys.exit()
donor, target = sys.argv[1:3]

if os.path.isfile(donor) and os.path.isfile(target):
    do_the_thing(donor, target)
elif os.path.isdir(donor) and os.path.isdir(target):
    namelist = [f for (_,_,fnames) in os.walk(target) for f in fnames]
    for name in namelist:
        donor_path = os.path.join(donor, name)
        target_path = os.path.join(target, name)
        if os.path.isfile(donor_path):
            do_the_thing(donor_path, target_path)
        else:
            print("\nCould not find a matching donor: " + name)
else:
    input(usage)
    sys.exit()