annotate fname

rmagick_drawtext_sample.rb

require 'RMagick'
include Magick

id_min = 0
id_max = 10

def annotate_id img, id
  fname = "Octcat_%03d.png" % id

  text = Draw.new
  text.font = '/System/Library/Fonts/Avenir Next.ttc'
  text.pointsize = 100
  text.gravity = CenterGravity

  text.annotate(img, 0,0,0,0, fname) {
     # 画像の色にかかわらず文字が読めるように縁取りする
     self.stroke_width = 3
     self.stroke = 'white'

     self.fill = 'gray30'
  }

  img.write(fname)
end

img = ImageList.new 'octcat.png'

id_min.upto(id_max) do |i|
  annotate_id img.copy, i
end