How to Render Blob Images in a Prawn Document

Is it possible to render blob images in a prawn document?

You should be able pass the image data as a StringIO

require 'stringio'
require 'pdf'

Prawn::Example.generate("foo.pdf") do |pdf|
  data = StringIO.new(render_my_image_to_a_string)
  pdf.image(data)
end

How to put an image on a label using Prawn/labels?

The answer appears to be to use something called StringIO, which apparently provides a File interface to an in-memory (blob) image.

So, I added the middle line, below:

    png = Barby::PngOutputter.new(tag[2]).to_png
    str_png = StringIO.new(png)
    pdf.image(str_png)

instead of trying to pass binary data via embed_image, and I am now getting the barcode in the final PDF output. (It still needs some tweaking, but the basic concept is now working.)

I had searched here many ways — really! But the word "blob" is what got the answer on this site.

Generating a PDF With Images from Base64 with Prawn

The Problem is, that the Api is returning this thing in UTF-8 - So I dont have a great choice.
Anyhow, I found this solution to be working

  file = Tempfile.new('labelimg', :encoding => 'utf-8')
  File.open(file, 'wb') do |f|
    f.write Base64.decode64(@image)
  end

why ruby prawn draw from bottom

This is because, as stated in the manual - https://github.com/prawnpdf/prawn/blob/c504ae4e683017d7afadece084734a9190230cd8/manual/basic_concepts/origin.rb#L5, PDF documents have their origin (0,0) at the bottom left of the page. Therefore when you specifically tell something to draw at [0,0] it will draw at the bottom left of its encapsualating bounding box, which in your case is the page.

How to save a base64 string as an image using ruby

When writing binary data to a file, such as is the case with an image, you cannot use text printing tools like IO#puts.

There's two things you need to ensure:

You need to be writing in binary mode to avoid any possible LF to CRLF expansion.
You must use write instead of puts as write can work on arbitrary data, but puts (literally "put string") is exclusively for text.

Combining these you get:

File.open('shipping_label.gif', 'wb') do |f|
  f.write(Base64.decode64(base_64_encoded_data))
end