Python script to convert any file to PNG and back, made just for fun

file_to_png.py

from sys import argv
from math import sqrt, ceil
from struct import pack, unpack
from PIL import Image

def file_to_image(data, ext):

    size = pack(">I", len(data))

    full_data = bytearray(ext + '\0', 'ascii') + size + data

    while len(full_data) % 4 != 0:
        full_data += bytearray('\0', 'ascii')

    width = ceil(sqrt(len(full_data) / 4))

    img_dest = Image.new('RGBA', (width, width))
    pixels = img_dest.load()

    for i in range(width):
        for j in range(width):
            
            pos = (i*width + j)*4

            if pos < len(full_data):
                pixels[j,i] = (full_data[pos], full_data[pos+1], 
                    full_data[pos+2], full_data[pos+3])
            else:
                pixels[j,i] = (0, 0, 0, 0)

    return img_dest

def image_to_file(img):

    pixels = img.load()
    data = bytearray()
    
    for i in range(img.width):
        for j in range(img.width):
             data.extend(pixels[j,i])

    ext = bytearray()
    byte = 0
    while byte < len(data) and data[byte] != 0:
        ext.append(data[byte])
        byte += 1
    ext = ext.decode('ascii')
    byte += 1
    size = unpack('>I', data[byte:byte+4])[0]
    byte += 4
    data = data[byte:byte+size]

    return data, ext

if len(argv) == 2:

    name = '.'.join(argv[1].split('.')[:-1])
    ext = argv[1].split('.')[-1]

    if ext == 'png':
        img = Image.open(argv[1])
        data, ext = image_to_file(img)

        with open(name + '_.' + ext, mode='wb') as file:
            file.write(data)

    else:
        with open(argv[1], mode='rb') as file:
            fileContent = file.read()

        img = file_to_image(fileContent, ext)
        img.save(name + '.png')