processor.rb

#Inside Photo model
has_attached_file :file, 
                    :processors => [ :blurplates, :thumbnail ],
                    :styles => { :frontpage => "460x100000", :view => "740x100000", :medium => '300x300', :thumb => "100x100>" }



#blurplates.rb
# Load libs
require 'camellia'
require 'RMagick'
#include RMagick
#include Camellia

module Paperclip
  # Handles thumbnailing images that are uploaded.
  class Blurplates < Processor
     
     def initialize(file, options = {}, attachment = nil)
       # Make the file available to this class
       @file = file   
       
       # Make an instance of the attachment available
       @attachment = attachment.instance
       
       # Make the basename of the file available
       @basename = File.basename(file.path, File.extname(file.path))
     end
     
     # Make will actually work on the file and then return it
     def make
       logger.debug "The wheels on the bus go round and round"
       # Create a new temporary file to work with
       dst = Tempfile.new([@basename, 'bmp'].compact.join("."))
       dst.binmode

       # Open up the image in ImageMagick to convert it to a bmp.
       image = Magick::Image.read(File.expand_path(file.path))  
       image.format = "BMP"
       image.write(File.expand_path(dst.path))      
       
       # Load image into Camellia
       carmage = CamImage.new
       carmage.load_bmp(File.expand_path(dst.path))
       yuv = image.to_yuv
       
       # consider only the V plane (red)
        yuv.set_roi(CamROI.new(3,0,0,yuv.width,yuv.height)) 

        # threshold and encode
        thr=yuv.encode_threshold(150)

        # labeling
        blobs=thr.labeling!
        #puts "#{blobs.nb_blobs} blobs detected"

        # draw rectangle on all detected blobs 
        blobs.each {|b| carmage.draw_rectangle(b.left,b.top,b.left+b.width-1,b.top+b.height-1,cam_rgb(255,0,0))}

        # save the resulting picture
        carmage.save_bmp(File.expand_path(dst.path))

        # find out the biggest blob
        sorted=blobs.sort {|a,b| b.surface<=>a.surface}
        #puts "The bigger blob is at position (#{sorted[0].cx},#{sorted[0].cy}) and its surface is #{sorted[0].surface}"
        
        # Load the image into ImageMagick again in order to convert it to a jpeg.
        lastImage = Magick::Image.read(File.expand_path(dst.path))
        lastImage.format = "JPG"
        lastImage.write(File.expand_path(dst.path))
        
        dst

     end
     
  end
  
end