How to convert a Base64 string to a pdf file using a shrimp gem

Question

I want to generate a pdf file from a DB record. Encode it into a Base64 string and store it in the database. Which works well. Now I want the opposite action, how can I decode the Base64 string and generate the pdf file again?

this is what i have tried so far.

 def data_pdf_base64 begin # Create Prawn Object my_pdf = Prawn::Document.new # write text to pdf my_pdf.text("Hello Gagan, How are you?") # Save at tmp folder as pdf file my_pdf.render_file("#{Rails.root}/tmp/pdf/gagan.pdf") # Read pdf file and encode to Base64 encoded_string = Base64.encode64(File.open("#{Rails.root}/tmp/pdf/gagan.pdf"){|i| i.read}) # Delete generated pdf file from tmp folder File.delete("#{Rails.root}/tmp/pdf/gagan.pdf") if File.exist?("#{Rails.root}/tmp/pdf/gagan.pdf") # Now converting Base64 to pdf again pdf = Prawn::Document.new # I have used ttf font because it was giving me below error # Your document includes text that not compatible with the Windows-1252 character set. If you need full UTF-8 support, use TTF fonts instead of PDF built-in fonts. pdf.font Rails.root.join("app/assets/fonts/fontawesome-webfont.ttf") pdf.text Base64.decode64 encoded_string pdf.render_file("#{Rails.root}/tmp/pdf/gagan2.pdf") rescue => e return render :text => "Error: #{e}" end end 

Now I am getting below the error:

ASCII-8BIT encoding cannot be transparently converted to UTF-8. Make sure that the encoding of the string you are trying to use is set correctly

I tried How to convert a base64 string to PNG using a shrimp without saving on the server in Rails , but this gives me an error:

"\ xFF" from ASCII-8BIT to UTF-8

Can someone point me what I am missing?

Answer 1

The answer is to decode Base64 encoding and send it directly or save it directly to disk (calling it as a PDF file, but without using shrimp).

The decoded string is a binary representation of the PDF file data, so there is no need to use shrimp or re-read the contents of the PDF data.

i.e.

  raw_pdf_str = Base64.decode64 encoded_string render :text, raw_pdf_str # <= this isn't the correct rendering pattern, but it good enough as an example. 

EDIT

To clarify some of the information provided in the comments:

• You can send a string as an attachment without saving it to disk using the render text: raw_pdf_str method render text: raw_pdf_str or #send_data (this is the 4.x API, I do not remember the API 5.x style).

• You can encode a string (from a Prawn object) without saving the rendered PDF data to a file (instead, save it to a String object). i.e:.

   encoded_string = Base64.encode64(my_pdf.render) 

• String data can be used directly as an email attachment, similar to the template given here , only using the string directly, instead of reading any data from a file. i.e:.

   # inside a method in the Mailer class attachments['my_pdf.pdf'] = { :mime_type => 'application/pdf', :content => raw_pdf_str }