hydra-derivatives
Derivative generation for hydra
If you have an ActiveFedora class like this:
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:
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'
transform_datastream :content, { :medium => "300x300>", :thumb => "100x100>" }
end
end
end
And you add some content to it:
obj = GenericFile.new
obj.content.content = File.open(...)
obj.mime_type = 'image/tiff'
obj.save
Then when you call obj.create_derivatives
a new datastream, called 'thumbnail' will have been created, with a downsized image in it.
We recommend you run obj.create_derivatives
in a background worker, because some derivative creation (especially videos) can take a long time.
You may want to adjust your path to add LibreOffice and Fits.sh support:
# in .bash_profile
export PATH=${PATH}:/Users/justin/workspace/fits-0.6.2:/Applications/LibreOffice.app/Contents/MacOS