simple captcha image generator in rmagick

captcha_image.rb

require 'rmagick'

module Captcha
  Image = Struct.new :text, :width, :height, :blur, :wave_length, :wave_amplitude do
    def image
      captcha_image = Magick::Image.new(width, height)
      captcha_text = Magick::Draw.new
      captcha_text.annotate(captcha_image, 0, 0, 0, height / 10, text) do
        self.gravity = Magick::CenterGravity
        self.pointsize = 60
        self.font_family = 'Arial'
        self.font_weight = Magick::BoldWeight
        self.fill = 'black'
      end
      captcha_image.wave(wave_amplitude, wave_length).transpose.wave(wave_amplitude, wave_length).transpose.radial_blur(blur)
    end

    def write
      file_name = ((0..5).map { Random.new.rand(0..9) } << '.png').join
      image.write(file_name)
      file_name
    end
  end
end

Captcha::Image.new('23 + 32 = ', 250, 100, 3, 100, 10).write