code: def base64_to_cv2(b64str: str):
      data = base64.b64decode(b64str.encode("utf8"))
      data = np.fromstring(data, np.uint8)
      data = cv2.imdecode(data, cv2.IMREAD_COLOR)
      return data
  
imports: import os
  import math
  import base64
  from typing import Callable
  import cv2
  import numpy
  import matplotlib
  from matplotlib import pyplot
  from matplotlib.figure import Figure
  from matplotlib.backends.backend_agg import FigureCanvasAgg
label_desc: Use image node_id 3 for calling a global function with example usage: base64_to_cv2(b64str) and returns: data