def window_level_values
      center = (self['0028,1050'].is_a?(Element) == true ? self['0028,1050'].value.to_i : nil)
      width = (self['0028,1051'].is_a?(Element) == true ? self['0028,1051'].value.to_i : nil)
      intercept = (self['0028,1052'].is_a?(Element) == true ? self['0028,1052'].value.to_i : 0)
      slope = (self['0028,1053'].is_a?(Element) == true ? self['0028,1053'].value.to_i : 1)
      return center, width, intercept, slope
    end
def window_level_values
      center = (self['0028,1050'].is_a?(Element) == true ? self['0028,1050'].value.to_i : nil)
      width = (self['0028,1051'].is_a?(Element) == true ? self['0028,1051'].value.to_i : nil)
      intercept = (self['0028,1052'].is_a?(Element) == true ? self['0028,1052'].value.to_i : 0)
      slope = (self['0028,1053'].is_a?(Element) == true ? self['0028,1053'].value.to_i : 1)
      return center, width, intercept, slope
    end
Collects the window level values needed to convert the original pixel
 values to presentation values.

 @note If some of these values are missing in the DObject instance,
   default values are used instead for intercept and slope, while center
   and width are set to nil. No errors are raised.
 @return [Array<Integer, NilClass>] center, width, intercept and slope