paper clip plugin validation fails

hallo friends i developpeda photo uploader using paper clip plugin its working quite well , but one problem is its able to upload all kinds of file. see i want only png,gif,jpeg and should show error message if validation fails.here if i applied validations in the model the result is errors like this

ArgumentError (too few arguments):   app/controllers/images_controller.rb:63:in `format'   app/controllers/images_controller.rb:63:in `create'   vendor/plugins/haml/rails/./lib/sass/plugin/rails.rb:19:in `process'   /usr/lib/ruby/1.8/webrick/httpserver.rb:104:in `service'   /usr/lib/ruby/1.8/webrick/httpserver.rb:65:in `run'   /usr/lib/ruby/1.8/webrick/server.rb:173:in `start_thread'   /usr/lib/ruby/1.8/webrick/server.rb:162:in `start'   /usr/lib/ruby/1.8/webrick/server.rb:162:in `start_thread'   /usr/lib/ruby/1.8/webrick/server.rb:95:in `start'   /usr/lib/ruby/1.8/webrick/server.rb:92:in `each'   /usr/lib/ruby/1.8/webrick/server.rb:92:in `start'   /usr/lib/ruby/1.8/webrick/server.rb:23:in `start'   /usr/lib/ruby/1.8/webrick/server.rb:82:in `start'   -e:4:in `load'   -e:4 here are my controller code

def create

    @user = @current_user.id     puts"usertrrrr"+@user.inspect     @image = Image.new(params[:image].merge(:user_id => @user))       if @image.save_with_permissions(params[:users])

         puts"if saved"

      else           puts"if not saved"          format.js # create.js.rjs          format.xml { render :xml => @image.errors, :status => :unprocessable_entity }         puts"hiiiiiiiiiiiiiiiiii"+@image.errors.inspect

      end       #puts"check the srrors are"+@image.errors.inspect      responds_to_parent { render } end

here is the model validation

validates_attachment_content_type :picture, :content_type=>['image/jpeg', 'image/png', 'image/gif'], :message => :missing_content_type

                       or   validates_format_of :picture,:allow_blank=>true, :with => %r{\.(gif|jpg|png|jpeg|bmp)$}i,:message => "Invalid file extension for teaser image. Please upload files with the following extensions only : .jpg, .jpeg, .png, .gif, .bmp"

can anyone help me to sort out this issue.please help me

Thanks In advance