Saving signatures has never been easier!

Add this line to your application's Gemfile:

gem 'john_hancock'

And then execute:

$ bundle

Or install it yourself as:

$ gem install john_hancock

With the gem installed, simply include it in the relevant JS manifest

//= require john_hancock

1. In config/initializers/assets.rb add:

Rails.application.config.assets.precompile += %w(john_hancock.js)

2. In config/importmap.rb add:

pin "john_hancock", to: 'john_hancock.js', preload: true

3. Lastly, in app/javascript/application.js:

import "john_hancock"

Then you are free to use it in the view

<%= form_for @user do |f| %>
  <%= f.signature_field :signature %>
  <%= f.submit %>
<% end %>

Once this is saved, you can output the string as an image.

<%= image_tag @user.signature %>

The signature_field method generates a canvas as well as a hidden field. If you would like more flexibility in the placement of these elements you can use them separately.

<%= form_for @user do |f| %>
  <%= f.signature_canvas %>
  <p>some text about the form</p>
  <%= f.hidden_signature_field :signature %>
  <%= f.submit %>
<% end %>

This gem is maintained by Brandon Lawrence and Ben Miller.

The underlying JS library, Signature Pad, is written by Thomas J Bradley.

Bug reports and pull requests are welcome on GitHub at https://github.com/Brantron/john_hancock.

The gem is available as open source under the terms of the MIT License.