require 'RMagick'
img = Magick::Image.read("images/Flower_Hat.jpg").first
begin
img = img.level_colors("green", "orange", true)
img.alpha(Magick::DeactivateAlphaChannel)
rescue NotImplementedError
not_imp = Magick::Image.read('images/notimplemented.gif').first
img = not_imp.resize(img.columns, img.rows)
end
img.write("level_colors.jpg")