code: def _cimss_true_color_contrast(img_data):
      """Perform per-chunk enhancement.
  
      Code ported from Kaba Bah's AWIPS python plugin for creating the
      CIMSS Natural (True) Color image in AWIPS. AWIPS provides that python
      code the image data on a 0-255 scale. Satpy gives this function the
      data on a 0-1.0 scale (assuming linear stretching and sqrt
      enhancements have already been applied).
  
      """
      max_value = 1.0
      acont = (255.0 / 10.0) / 255.0
      amax = (255.0 + 4.0) / 255.0
      amid = 1.0 / 2.0
      afact = amax * (acont + max_value) / (max_value * (amax - acont))
      aband = afact * (img_data - amid) + amid
      aband[aband <= 10 / 255.0] = 0
      aband[aband >= 1.0] = 1.0
      return aband
  
label_desc: Use image node_id 2 for calling a global function with example usage: _cimss_true_color_contrast(img_data) and returns: aband