code: def DQT(self, marker):
      #
      # Define quantization table.  Note that there might be more
      # than one table in each marker.
  
      # FIXME: The quantization tables can be used to estimate the
      # compression quality.
  
      n = i16(self.fp.read(2)) - 2
      s = ImageFile._safe_read(self.fp, n)
      while len(s):
          v = s[0]
          precision = 1 if (v // 16 == 0) else 2  # in bytes
          qt_length = 1 + precision * 64
          if len(s) < qt_length:
              msg = "bad quantization table marker"
              raise SyntaxError(msg)
          data = array.array(
              "B" if precision == 1 else "H", s[1:qt_length]
          )
          if sys.byteorder == "little" and precision > 1:
              data.byteswap()  # the values are always big-endian
          self.quantization[v & 15] = [data[i] for i in zigzag_index]
          s = s[qt_length:]
  
imports: import array
  import io
  import math
  import os
  import struct
  import subprocess
  import sys
  import tempfile
  import warnings
  from .None import Image, ImageFile
  from ._binary import i16be
  from ._binary import i32be
  from ._binary import o8
  from ._binary import o16be
  from .JpegPresets import presets
label_desc: Use image node_id 5 for calling a global function with example usage: DQT(marker) without return types