Question about Mini_Magick and mogrify

Hi.

I’m trying to write a caption to an image in my Rails Project.

From http://www.imagemagick.org this is something I should use:

width=identify -format %w dragon.jpg;
convert -background ‘#0008’ -fill white -gravity center -size
${width}x30
caption:“Faerie Dragons love hot apple pies!”
+size dragon.jpg +swap -gravity south -composite
anno_caption.jpg

If possible how can I write that in mini_magick? I thinks it’s related
to mogrify somehow.

Thanks.