resizing an image with rmagick

file.rb

require 'RMagick'

# http://www.imagemagick.org/RMagick/doc/comtasks.html#thumb

original_filename = 'image.jpg'
thumb_filename = 'thumb.jpg'

orig = Magick::Image.read(original_filename).first
rows, cols = [150, 150]

thumb = orig

# don't do a resize if original is already smaller than desired thumbnail size
if orig.rows > rows || orig.columns > cols
  thumb = orig.resize_to_fill(rows, cols)
end

thumb.write(thumb_filename) # {self.quality = 80}
thumb.destroy! if thumb != orig
orig.destroy!