old_contents: import logging
  
  
  logger = logging.getLogger(__name__)
  
  def crop_corners(image, box=None, **kwargs):
      """
      Crop corners to the selection defined by image_cropping
  
      `box` is a string of the format 'x1,y1,x2,y1' or a four-tuple of integers.
      """
      if isinstance(box, basestring):
          if box.startswith('-'):
              pass # TBC: what does this indicate? No-op value?
          else:
              try:
                  box = map(int, box.split(','))
              except (ValueError, IndexError):
                  # There's garbage in the cropping field, ignore
                  logger.warning(
                      'Unable to parse "box" parameter "%s". Ignoring.' % box)
  
      if isinstance(box, (list, tuple)):
          if len(box) == 4:
              if sum(box) < 0:
                  pass # TODO: add explanatory comment for this please
              else:
                  width = abs(box[2] - box[0])
                  height = abs(box[3] - box[1])
                  if width and height and (width, height) != image.size:
                      image = image.crop(box)
          else:
              logger.warning(
                  '"box" parameter requires four values. Ignoring "%r".' % (box,)
              )
  
      return image
  
  
new_contents: import logging
  
  
  logger = logging.getLogger(__name__)
  
  
  def crop_corners(image, box=None, **kwargs):
      """
      Crop corners to the selection defined by image_cropping
  
      `box` is a string of the format 'x1,y1,x2,y1' or a four-tuple of integers.
      """
      if box and not box.startswith('-'):
          # a leading - indicates that cropping is disabled
          try:
              box = map(int, box.split(','))
          except ValueError:
              # there's garbage in the cropping field, ignore
              logger.warning(
                  'Unable to parse "box" parameter "%s". Ignoring.' % box)
  
          if len(box) == 4:
              if sum(box) > 0:
                  # negative box values indicate that cropping is disabled
                  width = abs(box[2] - box[0])
                  height = abs(box[3] - box[1])
                  if width and height and (width, height) != image.size:
                      image = image.crop(box)
          else:
              logger.warning(
                  '"box" parameter requires four values. Ignoring "%r".' % box)
      return image
  
subject: Tweak thumbnail processor a little