attachment_fu rmagick on phusion passenger

Question

I am getting so much pain with setting up rmagick on Passenger . I’m developing a rails web application that has image processing feature using imagemagick. the image processing feature is working 100% on development using mongrel, but once i deploy it to production which uses phusion passenger I get the error

uninitialized constant Technoweenie::AttachmentFu::Processors::RMagickProcessor

i have successfully installed the following gems:

1.) rmagick (2.13.1) 2.) imagemagick

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this is the code from the model

has_attachment :content_type => :image,

             :storage => :file_system,
             :processor => 'Rmagick',
             :resize_to => '300 x 400',
             :max_size => 2.megabytes,
             :thumbnails => { :thumb => [85, 95], :geometry => 'x50'}

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