text: def write_png(buf, width, height):
      import zlib, struct
      width_byte_4 = width * 4
      raw_data = b"".join(b'\x00' + buf[span:span + width_byte_4] for span in range((height - 1) * width * 4, -1, - width_byte_4))
      def png_pack(png_tag, data):
          chunk_head = png_tag + data
          return struct.pack("!I", len(data)) + chunk_head + struct.pack("!I", 0xFFFFFFFF & zlib.crc32(chunk_head))
      return b"".join([
          b'\x89PNG\r\n\x1a\n',
          png_pack(b'IHDR', struct.pack("!2I5B", width, height, 8, 6, 0, 0, 0)),
          png_pack(b'IDAT', zlib.compress(raw_data, 9)),
          png_pack(b'IEND', b'')])
  