CODEWITHSUNDEEP
ruby-on-railsruby-on-rails-3amazon-s3paperclip
Sbbs
Sbbs

Reputation: 1670

Generate new style thumbnail based on existing style using Paperclip and aws-sdk

I have a Photo model that has 2 styles :original and :medium where :medium is a cropped version of the original. I would now like to add a :small style that's just a resized version of the :medium. For new images everything works: I just crop the original image twice, once for the :medium and once for the :small style. But I also have several thousand existing images that need to be reprocessed to have a :small thumb (all stored on AWS S3). Unfortunately, I can't just call .reprocess! :small since it will make small versions from the original, while I need small versions based on the cropped :medium version.

The medium versions have been cropped by users so I can't just reprocess the originals.

Is there an easy way to do this using Paperclip or do I have to write a script to pull the :medium version from S3, resize it locally and then ship it to the :small directory on S3?

UPDATE 1:

These are my styles

:original,  { geometry: "1500x1500>",                       format: :jpg },
:medium,    { geometry: "650x650#", processors: [:cropper], format: :jpg },
:small,     { geometry: "262x262#", processors: [:cropper], format: :jpg }

Notice that I've already added the :small style, but I still need to generate :small thumbs for images that have been created before this addition.

UPDATE 2: The way to do this it is probably using a rake task that would:

  1. fetch a :medium image from S3 for each photo that was created before :small style has been added
  2. resize it down to :small size
  3. upload the resulting image to /some/path/to/small/image/ on S3

Just not sure where to start.

Upvotes: 0

Views: 381

Answers (1)

NM Pennypacker
NM Pennypacker

Reputation: 6942

Looks like you could use a custom processor. In the past I've copied processors from paperclip and modified them to do what I need. For example if you take the thumbnail processor, modify it so that it crops your thumbnail and resizes it the way you want, and then save it as a custom processor (it should aotu-load if you put it in lib/paperclip).

Either way. Copy the file from https://github.com/thoughtbot/paperclip/blob/master/lib/paperclip/thumbnail.rb

Edit the section:

def transformation_command
  scale, crop = @current_geometry.transformation_to(@target_geometry, crop?)
  trans = []
  trans << "-coalesce" if animated?
  trans << "-auto-orient" if auto_orient
  trans << "-resize" << %["#{scale}"] unless scale.nil? || scale.empty?
  trans << "-crop" << %["#{crop}"] << "+repage" if crop
  trans << '-layers "optimize"' if animated?
 trans
end

to crop the image before you resize it. My gess is that you'll have to swap the resize and crop commands, but I'm not sure. All paperclip does is run imagemagick commands so you might find some good documentation here: http://www.imagemagick.org/script/command-line-processing.php

Save this as a custom processor in the lib/paperclip/your_processor_name.rb, and make whatever style you need style like this:

:original,  { geometry: "1500x1500>",                       format: :jpg },
:medium,    { geometry: "650x650#", processors: [:your_processor_name], format: :jpg },
:small,     { geometry: "262x262#", processors: [:your_processor_name], format: :jpg }

The bottom line is that you can only crop from an original, so if you need custom processing you have to build it. You'll have to play around with it, but this will get you on the right track.

Upvotes: 0

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