List layers without loading image?

[ChameleonScales]

Thanks, I went on IRC and Akkana Peck (akk) solved it!
Here is the result (it also prints out which is the active layer as a bonus):

Code:

#!/usr/bin/env python3

import sys


PROP_ACTIVE_LAYER = 2
PROP_VISIBLE      = 8
if __name__ == "__main__":
    filename = sys.argv[1]
    # open the file in readonly binary mode
    with open(filename, 'rb') as f:
        # go to the 30th bytes
        f.seek(30, 0)
        # read properties
        while True:
            prop_type = int.from_bytes(f.read(4), "big")
            prop_size = int.from_bytes(f.read(4), "big")
            f.read(prop_size)
            if prop_type == 0: #PROP_END
                break
        # read layers
        while True:
            next_layer_offset = int.from_bytes(f.read(8), "big")
            if not next_layer_offset: #end of layers offsets
                break;
            saved_pos = f.tell()
            f.seek(next_layer_offset + 12, 0)
            tmp = int.from_bytes(f.read(4), "big")
            name = f.read(tmp).decode("utf-8")
            print()
            print(name)
            while True:
                prop_type = int.from_bytes(f.read(4), "big")
                prop_size = int(int.from_bytes(f.read(4), "big") / 4)
                # print(prop_type, "size", prop_size)
                for i in range(prop_size):
                    lastint = int.from_bytes(f.read(4), "big")
                if prop_type == PROP_VISIBLE:
                    print("Visible? %x" % lastint)
                    break
                elif prop_type == PROP_ACTIVE_LAYER:
                    print("Active")
            f.seek(saved_pos, 0)