RMagick with ruby on rails , Reset Original picture

Question

I am using Rmagick in my photo sharing application and Its working properly , but while editing the picture ,my original picture get lost, I can't RESET the original picture , my code is given below .

image = Magick::ImageList.new("public/"+ @upload.public_filename(:org))
# image = image.colorize(0.30,0.30,0.30,"orange")
if params[:method] == "rotateacw"
  image   = image.rotate(-90)
elsif params[:method] == "rotatecw"      
  image = image.rotate(90)
elsif params[:method] == "black&white"      
  image = image.quantize(256, Magick::GRAYColorspace)
elsif params[:method] == "polaroid"    
  image = Magick::Image.read("public/"+ @upload.public_filename).first
  cols, rows = image.columns, image.rows
  image[:caption] = params[:polaroid_text].to_s
  image = image.polaroid {self.gravity = Magick::CenterGravity }

  image.change_geometry!("#{cols}x#{rows}") do |ncols, nrows, img|
    img.resize!(ncols, nrows)
  end
 image.write("public/" + @upload.public_filename(:org))

i want to have some code in the controller side , like Reset the same image , please help me out get original picture back ?