How to pass file url to helper method in middleman - ruby

Question

I'm writing a helper method to convert images to base64 strings when needed. Below is the code
# config.rb
helpers do
def base64_url(img_link, file_type: "jpg")
require "base64"
if file_type =="jpg"
"data:image/jpg;base64,#{Base64.encode64(open(img_link).to_a.join)}"
elsif file_type =="png"
"data:image/jpg;base64,#{Base64.encode64(open(img_link).to_a.join)}"
else
link
end
end
end
In page.html.erb
<%= image_tag base64_url('/images/balcozy-logo.jpg') %>
Now the problem is when ruby reads '/images/balcozy-logo.jpg' it reads the file from system root not from the root of the project.
Error message as follows
Errno::ENOENT at /
No such file or directory # rb_sysopen - /images/balcozy-logo.jpg
How do I get around this and pass proper image url from project_root/source/images

Answer 1

In Middleman app.root returns the root directory of the application. There's also app.root_path, which does the same but returns a Pathname object, which is slightly more convenient:
full_path = app.root_path.join("source", img_link.gsub(/^\//, ''))
The gsub is necessary if img_link starts with a /, since it would be interpreted as the root of your filesystem.
I've taken the liberty of making a few more revisions to your method:
require "base64"
helpers do
def base64_url(path, file_type: "jpg")
return path unless ["jpg", "png"].include?(file_type)
full_path = app.root_path.join("source", path.gsub(/^\//, ''))
data_encoded = File.open(full_path, 'r') do |file|
Base64.urlsafe_encode64(file.read)
end
"data:image/#{file_type};base64,#{data_encoded}"
end
end
I've done a few things here:
Moved require "base64" to the top of the file; it doesn't belong inside a method.
Check file_type at the very beginning of the method and return early if it's not among the listed types.
Instead of open(filename).to_a.join (or the more succinct open(filename).read), use File.open. OpenURI (which supplies the open method you were using) is overkill for reading from the local filesystem.
Use Base64.urlsafe_encode64 instead of encode64. Probably not necessary but it doesn't hurt.
Remove the unnecessary if; since we know file_type will be either jpg or png we can use it directly in the data URI.
There may be a more elegant way to get file_path or determine the file's MIME type using Middleman's built-in asset system, but a very brief search of the docs didn't turn anything up.