RMagic Error in rails, with AM Charts

I'm using AMCharts and rails. AMCharts uses the Image Magic lib to export an image of the chart. In rails this is done with the gem, RMagic.

In a controller this is implemented with the following controller method:

  def export
    width = params[:width].to_i
    height = params[:height].to_i
    data = {}
    img = Magick::Image.new(width, height)
    height.times do |y|
      row = params["r#{y}"].split(',')
      row.size.times do |r|
        pixel = row[r].to_s.split(':')
        pixel[0] = pixel[0].to_s.rjust(6, '0')
        if pixel.size == 2
          pixel[1].to_i.times do
            (data[y] ||= []) << pixel[0]
          end
        else
          (data[y] ||= []) << pixel[0]
        end
      end
      width.times do |x|
        img.pixel_color(x, y, "##{data[y][x]}")
      end
    end
    img.format = "PNG"
    send_data(img.to_blob , :disposition => 'inline', :type => 'image/png', :filename => "chart.png?#{rand(99999999).to_i}")
  end

When the controller is accessed however, I receive this error in the page:

The change you wanted was rejected.

Maybe you tried to change something you didn't have access to.

And this error in the logs (its running on heroku btw):

    ActionController::InvalidAuthenticityToken (ActionController::InvalidAuthenticityToken):
  /home/heroku_rack/lib/static_assets.rb:9:in `call'
  /home/heroku_rack/lib/last_access.rb:25:in `call'
  /home/heroku_rack/lib/date_header.rb:14:in `call'
  thin (1.0.1) lib/thin/connection.rb:80:in `pre_process'
  thin (1.0.开发者_开发百科1) lib/thin/connection.rb:78:in `catch'
  thin (1.0.1) lib/thin/connection.rb:78:in `pre_process'
  thin (1.0.1) lib/thin/connection.rb:57:in `process'
  thin (1.0.1) lib/thin/connection.rb:42:in `receive_data'
  eventmachine (0.12.6) lib/eventmachine.rb:240:in `run_machine'
  eventmachine (0.12.6) lib/eventmachine.rb:240:in `run'
  thin (1.0.1) lib/thin/backends/base.rb:57:in `start'
  thin (1.0.1) lib/thin/server.rb:150:in `start'
  thin (1.0.1) lib/thin/controllers/controller.rb:80:in `start'
  thin (1.0.1) lib/thin/runner.rb:173:in `send'
  thin (1.0.1) lib/thin/runner.rb:173:in `run_command'
  thin (1.0.1) lib/thin/runner.rb:139:in `run!'
  thin (1.0.1) bin/thin:6
  /usr/local/bin/thin:20:in `load'
  /usr/local/bin/thin:20

Rendering /disk1/home/slugs/149903_609c236_eb4f/mnt/public/422.html (422 Unprocessable Entity)

Anyone have any idea what's going on here?

I've figured it out:

added: require 'RMagick'

&

skip_before_filter :verify_authenticity_token

to my class