code: def extract_images_generic(pike, root, log, options):
      
  
      jpegs = []
      pngs = []
      for _, xref, ext in extract_images(pike, root, log, options, extract_image_generic):
          log.debug('xref = %s ext = %s', xref, ext)
          if ext == '.png':
              pngs.append(xref)
          elif ext == '.jpg':
              jpegs.append(xref)
      log.debug("Optimizable images: JPEGs: %s PNGs: %s", len(jpegs), len(pngs))
      return jpegs, pngs
docs: Extract any >=2bpp image we think we can improve