def write_pixels(bin)
      if self.exists?(PIXEL_TAG)
        # Update existing Data Element:
        self[PIXEL_TAG].bin = bin
      else
        # Create new Data Element:
        pixel_element = Element.new(PIXEL_TAG, bin, :encoded => true, :parent => self)
      end
    end
def write_pixels(bin)
      if self.exists?(PIXEL_TAG)
        # Update existing Data Element:
        self[PIXEL_TAG].bin = bin
      else
        # Create new Data Element:
        pixel_element = Element.new(PIXEL_TAG, bin, :encoded => true, :parent => self)
      end
    end
Transfers a pre-encoded binary string to the pixel data element, either by
 overwriting the existing element value, or creating a new "Pixel Data" element.

 @param [String] bin a binary string containing encoded pixel data