Activestorage Docx Previewer

activestorage_docx_previewer.rb

# lib/activestorage_docx_previwer

module ActiveStorage
  class Previewer::DocxPreviewer < Previewer
    class << self
      # also would be supported by unoconv
      # "application/vnd.openxmlformats-officedocument.wordprocessingml.document", "application/msword", "application/vnd.ms-powerpoint", "application/vnd.oasis.opendocument.text", "application/vnd.openxmlformats-officedocument.presentationml.presentation"
      def accept?(blob)
        blob.content_type == "application/vnd.openxmlformats-officedocument.wordprocessingml.document"
      end
    end

    def preview
      download_blob_to_tempfile do |input|
        draw_first_page_from input do |output|
          yield io: output, filename: "#{blob.filename.base}.png", content_type: "image/png"
        end
      end
    end

    private
      def draw_first_page_from(file, &block)
        draw 'unoconv', '-f', 'pdf', '-e', 'PageRange=1', '--stdout', file.path do |output_pdf|
          if File.size(output_pdf) > 0
            make_image_from_pdf(output_pdf, &block)
          end
        end
      end

      def make_image_from_pdf(output_pdf, &block)
        previewer = Rails.application.config.active_storage.previewers.find { |i|
          i.accept?(OpenStruct.new(content_type: 'application/pdf'))
        }
        previewer.new(blob).send(:draw_first_page_from, output_pdf, &block)
      end
  end
end

ActiveStorageDocxPreviewer.md

Docx (and other Office doc) previewer support for ActiveStorage

Converts all document formats using LibreOffice first to PDF and then to an image, using build-in pdf previwer of ActiveStorage

• needs: unoconv, a command line tool which uses libreoffice, e.g. apt install unoconv
• needs a PDF converter, because libreoffice will make a pdf from the office document, Mupdf oder Poppler are already integrated into ActiveStorage, and poppler is free to use, e.g. apt install poppler-utils

initializer.rb

# config/initializers/active_storage.rb
require 'activestorage_docx_previewer'

Rails.application.config.active_storage.previewers << ActiveStorage::Previewer::DocxPreviewer

Line 32 works only as: previewer.new(blob).send(:draw_first_page_from, output_pdf, &block)

That code is from a working Rails 5.2 app, I didn't test it with Rails 6 yet.
Yes, one has to pass a Blob, but just passing nil as that blob worked at least in the 5.2.

yes on Rails 6.0.1 it needs blob, because pdf previewer calls blob.key in its implemetation

@zealot128 Thanks for sharing!

@durcak Thanks for the Rails 6 fix!