How to render images from Markdown files with Rails 5.2? - ruby-on-rails

Question

I based my applications inline help on Markdown files, implemented with Redcarpet gem. Contextual help is displayed as expected, but embedded images are not.
The help files structure in the project is:
public/help/administration/Connection
- Business_resources_hierarchy.png
- connections-fr.md
The connection-fr.md files contains:
# CONNECTIONS
Décrit la gestion des connexions aux ressources de l'infrastructure informatique.
## Principe de fonctionnement
La connaissance des ressources techniques comporte un certain niveau de complexité :
* adresses IP et protocoles des services
* login et mot de passe des utilisateurs techniques
* droits d'utilisation de la ressource
* multipliés par le nombre d'environnements déployés dans l'organisation (Dev, Test, Prod ...)
La gestion des connexions permet au métier de s'affranchir de cette complexité en offrant une vue métier des ressources nécessaires à la production statistique au travers d'une hiérarchie :
![Hiérarchie des resources métiers](Business_resources_hierarchy.png)
## Eléments d'infrastructure
1. Les ressources métiers - offrent une vue fonctionnelle des
Markdown is supported by the application_helper.rb:
module ApplicationHelper
### Implementing Help files management with Markdown
def markdown
markdown = Redcarpet::Markdown.new(Redcarpet::Render::HTML, :autolink => true, :space_after_headers => true, tables: true)
end
def displayHelp
puts "Help requested for: #{params[:page_name]}.#{params[:format]}"
# Parse the request from the page -> namespace/class/controller
if params[:page_name].index('/')
domain = params[:page_name].split('/')[0]
page = params[:page_name].split('/')[1]
else
domain = ''
page = params[:page_name]
end
method = params[:format] # The method from the controller is not used yet
# Build the help file path and name using the current locale
case page
when 'Change_Log' # Does it still exist?
filename = File.join(Rails.root, 'public', "CHANGELOG.md")
when 'Release_notes' # Does it still exist?
filename = File.join(Rails.root, 'public', "Release_notes.md")
else
filename = File.join(Rails.root,
'public',
'help',
domain,
page.classify,
"#{page}-#{I18n.locale.to_s[0,2]}.md"
)
end
puts "Requested help file: #{filename}"
if not File.file?(filename)
filename = File.join(Rails.root, 'public', 'help', "help-index-#{I18n.locale.to_s[0,2]}.md")
end
begin
file = File.open(filename, "rb")
markdown.render(file.read).html_safe.force_encoding('UTF-8')
rescue Errno::ENOENT
render :file => "public/404.html", :status => 404
end
end
end
I tried a few ways to define the path to the image file, but it does not show up. When submitting the file URL to Rails, it raises the following error:
No route matches [GET] "/Business_resources_hierarchy.PNG"
How to define the path to the file, or configure the helper so that the image is displayed?