code: def get_cropping_offset(crop, epsilon):
      
      m = _CROP_PERCENT_PATTERN.match(crop)
      if not m:
          raise ThumbnailParseError('Unrecognized crop option: %s' % crop)
      value = int(m.group('value')) # we only take ints in the regexp
      unit = m.group('unit')
      if unit == '%':
          value = epsilon * value / 100.0
          # return ∈ [0, epsilon]
      return int(max(0, min(value, epsilon)))
docs: Calculates the cropping offset for the cropped image. This only calculates
      the offset for one dimension (X or Y). This should be called twice to get
      the offsets for the X and Y dimensions.
  
      :param str crop: A percentage cropping value for the plane. This is in the
          form of something like '50%'.
      :param float epsilon: The difference between the original image's dimension
          (X or Y) and the desired crop window.
      :rtype: int
      :returns: The cropping offset for the given dimension.