hydra-derivatives
Derivative generation for hydra
If you have an ActiveFedora class like this: ```ruby class GenericFile < ActiveFedora::Base include Hydra::Derivatives
has_file_datastream :content
attr_accessor :mime_type
# Use a block to declare which derivatives you want to generate
makes_derivatives do |obj|
case obj.mime_type
when 'application/pdf'
obj.transform_datastream :content, { :thumb => "100x100>" }
when 'audio/wav'
obj.transform_datastream :content, { :mp3 => {format: 'mp3'}, :ogg => {format: 'ogg'} }, processor: :audio
when 'video/avi'
obj.transform_datastream :content, { :mp4 => {format: 'mp4'}, :webm => {format: 'webm'} }, processor: :video
when 'image/png', 'image/jpg'
obj.transform_datastream :content, { :medium => "300x300>", :thumb => "100x100>" }
end
end
end ```
Or a class like this:
```ruby class GenericFile < ActiveFedora::Base include Hydra::Derivatives
has_file_datastream :content
attr_accessor :mime_type
# Use a callback method to declare which derivatives you want
makes_derivatives :generate_derivatives
def generate_derivatives
case mime_type
when 'application/pdf'
transform_datastream :content, { :thumb => "100x100>" }
when 'audio/wav'
transform_datastream :content, { :mp3 => {format: 'mp3'}, :ogg => {format: 'ogg'} }, processor: :audio
when 'video/avi'
transform_datastream :content, { :mp4 => {format: 'mp4'}, :webm => {format: 'webm'} }, processor: :video
when 'image/png', 'image/jpg', 'image/tiff'
transform_datastream :content, { :medium => "300x300>", :thumb => {size: "100x100>", datastream: 'thumbnail'} }
end
end
end ```
And you add some content to it:
ruby
obj = GenericFile.new
obj.content.content = File.open(...)
obj.mime_type = 'image/tiff'
obj.save
Then when you call obj.create_derivatives
two new datastreams, ‘thumbnail’ and ‘content_medium’, will have been created with downsized images in them.
We recommend you run obj.create_derivatives
in a background worker, because some derivative creation (especially videos) can take a long time.
Installation
Just add gem 'hydra-derivatives'
to your Gemfile.
Dependencies
To enable LibreOffice, FFMpeg and Fits.sh support, you make sure they are on your path. Most people will put that in their .bash_profile or somewhere similar. For example:
bash
# in .bash_profile
export PATH=${PATH}:/Users/justin/workspace/fits-0.6.2:/Applications/LibreOffice.app/Contents/MacOS
Alternatively, you can configure their paths: ```ruby Hydra::Derivatives.ffmpeg_path = ‘/opt/local/ffmpeg/bin/ffmpeg’ Hydra::Derivatives.fits_path = ‘/opt/local/fits/bin/fits.sh’ Hydra::Derivatives.libreoffice_path = ‘/opt/local/libreoffice_path/bin/soffice’
```