如何从回形针附加的图像中读取exif数据？

Question

I'm trying to read the exif data from jpeg images that I upload with paperclip using the exifr gem and save focal length, etc to attributes but I can't seem to do it. I'm a rails beginner and would be most appreciative if anyone could assist.

my photo.rb model:

class Photo < ActiveRecord::Base

attr_accessible :date, :exif, :name, :photo
has_attached_file   :photo, :styles => { :small => "200x200#" , :medium => "1280x720#" },
:url  => "/assets/photos/:id/:style/:basename.:extension",
:path => ":rails_root/public/assets/photos/:id/:style/:basename.:extension"

after_photo_post_process :load_exif

validates_attachment_presence :photo
validates_attachment_content_type :photo, :content_type => ['image/jpeg']



def load_exif
  exif = EXIFR::JPEG.new(photo.queued_for_write[:original])
  return if exif.nil? or not exif.exif?
  self.exposure = exif.exposure_time.to_s
  self.f_stop = exif.f_number.to_f.to_s
  self.focal_length = exif.focal_length.to_f.round.to_s
  self.iso = exif.iso_speed_ratings
  self.date = exif.date_time.to_date
  rescue
    false
  end
end

my form (using SimpleForm):

<%= simple_form_for @photo, :html => {:multipart => true}  do |f| %>
  <%= f.error_notification %>

  <div class="form-inputs">
    <%= f.input :name %>
    <%= f.file_field :photo, :label => 'Attach photo' %>
  </div>

  <div class="form-actions">
    <%= f.button :submit %>
  </div>
<% end %>

show.html.erb with fields I'm trying to show:

<p>
  <b>Name:</b>
  <%= @photo.name %>
</p>

<p>
  <b>Date:</b>
  <%= @photo.date %>
</p>

<p>
  <b>Exposure:</b>
  <%= @photo.exposure %>
</p>

I'm probably missing something stupid so I apologize if that's so.

Answer 1

Try changing the first line in your load_exif method to:

exif = EXIFR::JPEG.new(photo.queued_for_write[:original].path)

Without .path on the end, I don't believe it's returning the file path.