Today I Learned

A JetRockets project

3 posts by Dmitry Voronov @dmdropkick

Usage image files from S3 in WickedPdf

If you need to use image files from S3 in your generated pdf file using WickedPdf, then you need to first upload the image. You can create method that does this and add it to the helper.

require 'open-uri'

module PdfHelper
  def embed_remote_image(url, content_type)
    asset = open(url, "r:UTF-8", &:read)
    base64 = Base64.encode64(asset.to_s).gsub(/\s+/, "")
    "data:#{content_type};base64,#{Rack::Utils.escape(base64)}"
  end
end

And use image_tag instead of wicked_pdf_image_tag

= image_tag embed_remote_image(file.logo_url, 'image/jpeg')

How to create zip files on the fly w/o Tempfile

There are many articles about how to archive files from the server and send a zip-file to a client without persisting it on the server. But usually they don’t literally do it, because they use temporary files.

There is a simple way to do it without creating any file though. You just have to put files directly to Zip::OutputStream and then read from it. Btw pay attention: you must rewind the stream before reading it.

# some files objects
def download(files)
  zip_stream = Zip::OutputStream.write_buffer do |zip|
    files.each.with_index(1) do |file, index|
     # file name must be uniq in archive
      zip.put_next_entry("#{file.name}--#{index}.#{file.extension}")
      zip.write(file.read.force_encoding('utf-8'))
    end
  end
  # important - rewind the steam
  zip_stream.rewind
  send_data zip_stream.read, 
            type: 'application/zip', 
            disposition: 'attachment', 
            filename: 'files-archive.zip'
end