How to reduce dpi to 72 for thumbs in paperclip, originals are 300 - rails 3.2

Question

Other posts claim that paperclip reduces dpi to 72 when processing, but this is not true. Out of the box, it leaves dpi untouched. I need 300dpi originals in print quality, but the thumbs should be 72dpi for monitor. How can I do this (whilst processing the upload)?

Answer 1

has_attached_file :uploadedPhoto, 
                  :styles          => {:portrait => "400x", :icon => "32x32#"},
                  :convert_options => {:portrait => '-strip -quality 60', :icon => '-strip -quality 60' }