FileColumn: regenerate images

If you change the images dimensions or introduce a new version for models using file column you need a way to update the existing ones.
Here is a script that will regenerate all file column images and its version. We still look for a way to generate only new versions.

# recreates all file_column images in all needed sizes
class ImageUpdater
  
  def update_all
    update_model(:user, :photo)
    update_model(:auto, :photo)
    update_model(:photo, :file)
    update_model(:group, :photo)
  end
  
  private
  
  def update_model(class_name, attribute_name)
    eval(class_name.to_s.capitalize).find(:all).each {|instance|
      begin
        dir = instance.send(attribute_name)
        unless dir.blank?
          instance.send("#{attribute_name}=", upload(dir))
          instance.save!
        end
      rescue Exception => e
        puts e.message
      end
    }
  end
  
  # copied from file_column/test_case.rb
  def upload(path, content_type=:guess, type=:tempfile)
    if content_type == :guess
      case path
        when /\.jpg$/ then content_type = "image/jpeg"
        when /\.png$/ then content_type = "image/png"
        else content_type = nil
      end
    end
    uploaded_file(path, content_type, File.basename(path), type)
  end
    
  def uploaded_file(path, content_type, filename, type=:tempfile) # :nodoc:
    if type == :tempfile
      t = Tempfile.new(File.basename(filename))
      FileUtils.copy_file(path, t.path)
    else
      if path
        t = StringIO.new(IO.read(path))
      else
        t = StringIO.new
      end
    end
    (class << t; self; end).class_eval do
      alias local_path path if type == :tempfile
      define_method(:local_path) { "" } if type == :stringio
      define_method(:original_filename) {filename}
      define_method(:content_type) {content_type}
    end
    return t
  end
    
end

Tags: file_column, rails, regnerate-images, script

This entry was posted on Sunday, August 12th, 2007 at 12:29 am by Thilo Utke. You can follow any responses to this entry through the RSS 2.0 feed. You can leave a response, or trackback from your own site.

7 Responses to “FileColumn: regenerate images”

Marc Says:
August 19th, 2007 at 8:30 pm
Great workaround Thilo!

I apologize if this is a trivial question, but how would one integrate this into their Rails site? It seems like there would be several possibilities, so how would you do it?
Thilo Says:
August 21st, 2007 at 9:09 am
We don’t integrate the script in our site. We ran it on demand. Because it regnerate all images. This puts serious load on our serve ran took a couple of days.

If you need new inmage versions on demand it is better to use: url_for_image_column. It checks if a version exitst and renerate it if not. But it can’t update geometrie of existing versions. Hope that helps.
Marc Says:
August 25th, 2007 at 9:04 am
Thanks Thilo!

I had never heard of url_for_image_column before. Once I started searching for it, the only good documentation I found was in the source files themselves. That has accomplished exactly what I needed.
Homan Says:
September 6th, 2007 at 11:32 pm
There are some conditions as to whether url_for_image_column will regenerate a new image version on the fly. File_column places the master version in the directory:

model_name/column_name/record_id/image_name.ext

Alternate named versions like ‘thumb’ will be placed in the same directory but in a folder of the same version name:

model_name/column_name/record_id/thumb/image_name.ext

Now, if you delete the image in the thumb directory, no new image will be regenerated. You just get a broken link. If however, you delete the thumb directory entirely, url_for_image_column will attempt to generate a new named version for you. However, it is not smart enough to determine the size from the versions information defined in the model, you must specify the crop and size options in the url_for_image_column parameters.
thilo Says:
September 7th, 2007 at 11:13 am
Hi Homan, thanks for your insight. Are u sure that it can’t access the version information? Because I have to provide the model object anyway (e.g. url_for_image_column(@auto, ‘photo’, :badge_5) . And as far a I can see it always ends up in create_magick_version_if_needed. And it works just fine for us, deleting just specific versions. Because it checks each version, as it can be seen in the above mentioned method, here ‘File.exists?(absolute_path(version_options[:name]))’. We just use it in one case, so maybe it just works by coincident. But I hope not
Sascha Says:
February 6th, 2008 at 3:31 pm
I changed class_name.to_s.capitalize to class_name.to_s.classify, because calling update_model(:common_page_asset, :asset) was not working with capitalize. Maybe i misunderstood your parameter convention or the script has to be changed when using model names with underscores. However, thanks for the script!
Alexander Lang Says:
February 10th, 2008 at 9:49 pm
i think you are right. capitalize works as long as the class name only consists of one word, which has been the case for all our classes so far.

FileColumn: regenerate images

7 Responses to “FileColumn: regenerate images”

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