code: def get_active_img_fil(img):
      mat = img.astype(np.float32)
      mat[mat < 0.18] = 0
      mat = -mat + 1
      mat = mat * 255.0
      mat[mat < 0] = 0
      mat[mat > 255] = 255
      mat = mat.astype(np.uint8)
      return mat
  
imports: import numpy
  import cv2
  from scipy import ndimage
label_desc: Use image node_id 17 for calling a global function with example usage: get_active_img_fil(img) and returns: mat