Question

I’m using the Paperclip gem with a Rails 3.1.1 app. It’s working as advertised and expected. I would like to use the imagemagick -liquid-rescale delegate, however. According to the imagemagick documentation (which I tried in terminal.app), this works:

convert logo_trimmed.jpg  -liquid-rescale 75x100%\!  logo_lqr.jpg

I tried a variation…

convert my_pic.jpg -liquid-rescale 60x60\! my_new_pic.jpg

That worked as expected, too. I’ve tried several permutations in my Image model in my rails app, but I cannot get Paperclip to invoke liquid-rescale. My latest attempt was:

has_attached_file :pic, :styles => {:square => "-liquid-rescale 60x60\!" }

This fails without an error message, merely duplicating the original image with a new name.

How do I instruct paperclip to invoke liquid-rescale?

Answer 1

Here’s what I did. I had to write a custom processor, which I named liquid.In the model:

has_attached_file :pic, :styles => {:square => {:processors =>[:liquid],:geometry => "60x60>"} }

I’m not sure whether the :geometry option is necessary, but I added it because thumbnail.rb in the paperclip gem says that it’s not optional.

I then added a file: /my_app/lib/paperclip_processors/liquid.rb with contents:

module Paperclip
    class Liquid < Thumbnail
        def transformation_command
            "-resize '60x60>' -liquid-rescale '60x60!'"
        end
    end
end

Finally, I ran the following in the console:

Image.all.each {|i| i.pic.reprocess!}

That did the trick.