Java ColorConvertOp in JRuby

jruby_color_convertop.rb

case @data
   when "GrayScale"
      colorSpace = CS.getInstance(CS::CS_GRAY)
      op = java.awt.image.ColorConvertOp.new(colorSpace, nil)
   when "Negative"
      lut = Array.new
      for j in 0..255
         lut[j] = 256-j
      end
      jlut = lut.to_java :byte
      blut = java.awt.image.ByteLookupTable.new(0, jlut)
      op = java.awt.image.LookupOp.new(blut, nil)
   when "Brighten"
      op = java.awt.image.RescaleOp.new(1.4, -25, nil)
   when "Sharpen"
      data = [-1, 0, -1, 0, 5, 0, -1, 0, -1]
      dataFloat = data.to_java :float
      sharpen = java.awt.image.Kernel.new(3, 3, dataFloat)
      op = java.awt.image.ConvolveOp.new(sharpen)
end