How To Implement Paperclip in Rails

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In this article, we’ll show you how to use Paperclip in Rails to add images processing them.

Paperclip is a gem used for image processing in Ruby. It is one of the most popular image processing gems and has been used by projects like GitHub, Shutterstock, and thoughtbot.

How to install Paperclip

To install Paperclip, add it to your Gemfile and run the bundle command to install it.

gem "paperclip", "~> 5.1.0"

How to use Paperclip

Paperclip is typically used with ActiveRecord, so we’ll use it with a Ruby on Rails project.

First, we need to generate a model to store the image. We’ll use the rails generate command to generate a model with an avatar field.

rails generate model User avatar

This will generate a model with a has_attached_file :avatar line and a migration to add an avatar_file_name field to the database.

How to add an avatar to a User

Next, we need to add an avatar field to our form so that users can upload an image.

We can use the file_field helper to do this.

<%= form_for @user do |f| %>
  <%= f.file_field :avatar %>
  <%= f.submit %>
<% end %>

This will add a file upload field to our form.

How to upload an avatar

Now we can upload an image, but we need to process it with Paperclip first.

In our controller, we can add a before_action to process the uploaded image.


class UsersController < ApplicationController
  before_action :set_user, only: [:show, :edit, :update, :destroy]
  before_action :upload_avatar, only: [:create, :update]

  def new
    @user = User.new
  end

  def create
    @user = User.new
    if @user.save
      redirect_to @user
    else
      render :new
    end
  end

  def upload_avatar
    if params[:user][:avatar]
      @user.avatar = params[:user][:avatar]
    end
  end
end

We need to whitelist the avatar field in our controller as well.

class UsersController < ApplicationController
  before_action :set_user, only: [:show, :edit, :update, :destroy]
  before_action :upload_avatar, only: [:create, :update]

  def user_params
    params.require(:user).permit(:avatar)
  end
end

Now we can upload an image, which will be processed with Paperclip.

How to add image processing to Paperclip

Paperclip can do a lot more than just uploading images. It can also resize, crop, and watermark images.

To do this, we need to add some processing options to our model.

class User < ApplicationRecord
  has_attached_file :avatar, styles: {
    thumb: "100x100>",
    medium: "300x300>",
    large: "600x600>"
  }
end

This will generate three versions of the image (thumb, medium, and large) and resize them to fit within the given dimensions.

We can also crop images.

class User < ApplicationRecord
  has_attached_file :avatar, styles: {
    thumb: ["100x100#", :png],
    medium: ["300x300#", :jpg],
    large: ["600x600#", :png]
  }
end

This will create three versions of the image (thumb, medium, and large) and crop them to fit within the given dimensions.

We can also watermark images.

class User < ApplicationRecord
  has_attached_file :avatar, styles: {
    thumb: { geometry: "100x100#", format: :png, convert_options: "-background '#000C' -gravity center -composite -depth 8" },
    medium: { geometry: "300x300#", format: :jpg, convert_options: "-background '#000C' -gravity center -composite -depth 8" },
    large: { geometry: "600x600#", format: :png, convert_options: "-background '#000C' -gravity center -composite -depth 8" }
  }
end

This will create three versions of the image (thumb, medium, and large) and watermark them with the given image.

How to validate images with Paperclip

We can also validate images with Paperclip.

class User < ApplicationRecord
  has_attached_file :avatar
  validates_attachment_content_type :avatar, content_type: /\Aimage\/.*\z/
end

This will validate that the uploaded image is an image.

We can also validate the file size.

class User < ApplicationRecord
  has_attached_file :avatar
  validates_attachment_content_type :avatar, content_type: /\Aimage\/.*\z/
  validates_attachment_size :avatar, in: 0..5.megabytes
end

This will validate that the uploaded image is in the given range (0 to 5 MB).

How to use Paperclip with S3 We can also use Paperclip with S3 for storage.

First, we need to add the aws-sdk gem to our Gemfile.

gem "aws-sdk"

Next, we need to configure Paperclip to use S3 for storage. We can do this in an initializer.

Paperclip::Attachment.default_options[:storage] = :s3
Paperclip::Attachment.default_options[:s3_protocol] = "https"
Paperclip::Attachment.default_options[:s3_credentials] = {
  bucket: ENV["S3_BUCKET_NAME"],
  access_key_id: ENV["AWS_ACCESS_KEY_ID"],
  secret_access_key: ENV["AWS_SECRET_ACCESS_KEY"],
  s3_region: ENV["AWS_REGION"],
}

We need to set the :s3_protocol to https because S3 doesn’t support HTTP.

We also need to set the :s3_credentials to our S3 credentials. We can set these in our .env file.

S3_BUCKET_NAME=your-bucket-name
AWS_ACCESS_KEY_ID=your-access-key-id
AWS_SECRET_ACCESS_KEY=your-secret-access-key
AWS_REGION=your-region

Now Paperclip will upload files to S3 instead of the local filesystem.

How to delete images with Paperclip

We can also delete images with Paperclip.

class User < ApplicationRecord
  has_attached_file :avatar
  before_destroy :destroy_avatar

  def destroy_avatar
    self.avatar = nil
  end
end

This will delete the image from S3 when the User is destroyed.

We can also delete the image from the local filesystem.

class User < ApplicationRecord
  has_attached_file :avatar, styles: {
    thumb: { geometry: "100x100#", format: :png, convert_options: "-background '#000C' -gravity center -composite -depth 8" },
    medium: { geometry: "300x300#", format: :jpg, convert_options: "-background '#000C' -gravity center -composite -depth 8" },
    large: { geometry: "600x600#", format: :png, convert_options: "-background '#000C' -gravity center -composite -depth 8" }
  }
  before_destroy :destroy_avatar

  def destroy_avatar
    self.avatar.destroy
  end
end

This will delete the image from the local filesystem when the User is destroyed.

How to use Paperclip with a CDN

We can also use Paperclip with a CDN.

Paperclip::Attachment.default_options[:url] = ":s3_domain_url"
Paperclip::Attachment.default_options[:path] = "/:class/:attachment/:id_partition/:style/:filename"

Paperclip::Attachment.default_options[:s3_host_name] = "s3-#{ENV['AWS_REGION']}.amazonaws.com"

This will configure Paperclip to use a CDN.

Conclusion

Paperclip is a great gem for image processing in Ruby. It can upload, resize, crop, and watermark images.

For more information on the Paperclip, check out the paperclip GitHub page.