完整代码如下：

from glob import glob
import os
from tqdm import tqdm


def get_sign(dat_r):
    signatures = [(0x89, 0x50, 0x4e), (0x47, 0x49, 0x46), (0xff, 0xd8, 0xff)]
    mats = [".png", ".gif", ".jpg"]
    for now in dat_r:
        for j, xor in enumerate(signatures):
            res = [nowByte ^ xor_byte for nowByte,
                   xor_byte in zip(now[:3], xor)]
            if res[0] == res[1] == res[2]:
                return res[0], mats[j]
    else:
        raise Exception("no valid signature is found")


def imageDecode(file, root_path, dest_path=None):
    dat_r = open(file, "rb")
    try:
        sign, mat = get_sign(dat_r)
        dat_r.seek(0)
        data = bytes(byte ^ sign for byte in dat_r.read())
        relative_path = os.path.relpath(file, root_path)
        if dest_path is None:
            dest_path = os.path.join(root_path, "CovertImage")
        dest = os.path.join(dest_path,
                            relative_path.replace(".dat", mat))
        os.makedirs(os.path.dirname(dest), exist_ok=True)
        with open(dest, "wb") as write:
            write.write(data)
    finally:
        dat_r.close()


def main(into_path, out_path=None):
    for file in tqdm(glob(os.path.join(into_path, "**", "*.dat"), recursive=True)):
        imageDecode(file, into_path, out_path)
        
if __name__ == '__main__':
    into_path = r"D:\tmp\wx_icon_dat"
#     out_path = r"D:\tmp\wx_icon_dat"
    main(into_path, out_path=None)

支持递归处理，不指定结果文件夹时，结果将写入into_path+"CovertImage"目录下。
还原示例：