title: paperclip error while reporcessing after rails 3 upgrade
body: <p>I have paperclip working uploading and saving different styles for images but when i go to crop the image using jcrop from railscasts tutorial it doesnt crop image.   I get this error</p>
  
  <pre><code>[paperclip] identify -format %wx%h '/var/folders/z+/z+KzOZBFE9irCpbMKKBGFk+++TI/-Tmp-/paperclip-reprocess20110118-19757-1wtrjaj-0[0]' 2&gt;/dev/null
  [paperclip] convert '/var/folders/z+/z+KzOZBFE9irCpbMKKBGFk+++TI/-Tmp-/paperclip-reprocess20110118-19757-1wtrjaj-0[0]' -crop 28x32+13+15-resize "400x400&gt;" '/var/folders/z+/z+KzOZBFE9irCpbMKKBGFk+++TI/-Tmp-/paperclip-reprocess20110118-19757-1wtrjaj-020110118-19757-1a5n558-0.jpg' 2&gt;/dev/null
  [paperclip] An error was received while processing: #&lt;Paperclip::PaperclipError: There was an error processing the thumbnail for paperclip-reprocess20110118-19757-1wtrjaj-0&gt;
  </code></pre>
  
  <p>This was working in rails 2.3.9 but hvae just upgraded to rails 3.0.3    I have got all latest gems etc.</p>
  
  <p>The cropper.rb file is as follows and is in the initializers dir</p>
  
  <pre><code>module Paperclip
    class Cropper &lt; Thumbnail
      def transformation_command
        if crop_command
          crop_command + super.join(" ").sub(/ -crop \S+/, '')
        else
          super
        end
      end
  
      def crop_command
        target = @attachment.instance   
  
        if target.cropping?
          " -crop #{target.crop_w.to_i}x#{target.crop_h.to_i}+#{target.crop_x.to_i}+#{target.crop_y.to_i}"
        end
      end
    end
  end
  </code></pre>
  
  <p>The sizes are getting into this but no actually cropping the image.</p>
  
  <p>Please can anyone help with this ?</p>
  
  <p>thanks alot
  Richard Moss</p>