CarrierWave extension to crop uploaded images using Jcrop plugin with preview.

Install the latest stable release:

$[sudo] gem install carrierwave-crop

In Rails, add it to your Gemfile:

gem 'carrierwave-crop'

And then execute:

$ bundle

Finally, restart the server to apply the changes.

Add the required files in assets

In application.js

//= require jquery
//= require jquery.jcrop

In application.css

*= require jquery.jcrop

Generate a coffeescript for cropping:

rails generate cropper user avatar

this should give you a file in:

app/assets/javascripts/users.js.coffee

Open your model file and add the cropper:

class User < ActiveRecord::Base
  mount_uploader :avatar, AvatarUploader
  crop_uploaded :avatar  ## Add this
end

Render a view after creating/updating a user, add a crop action in your controller. For example:

def create
  @user = User.new(user_params)
  respond_to do |format|
    if @user.save
      format.html {
        if params[:user][:avatar].present?
          render :crop  ## Render the view for cropping
        else
          redirect_to @user, notice: 'User was successfully created.'
        end
      }
      format.json { render action: 'show', status: :created, location: @user }
    else
      format.html { render action: 'new' }
      format.json { render json: @user.errors, status: :unprocessable_entity }
    end
  end
end

For Rails 4.x, whitelist the cropping attributes - fieldname_crop_x, fieldname_crop_y, fieldname_crop_w, fieldname_crop_h.

For example:

def user_params
  params.require(:user).permit(:avatar_crop_x, :avatar_crop_y, :avatar_crop_w, :avatar_crop_h, ....)
end

In the view, say crop.html.erb:

<%= form_for @user do |f| %>
  <%= f.cropbox :avatar %>
  <%= f.previewbox :avatar %>
  <%= f.submit 'Crop' %>
<% end %>

In the carrierwave uploader, say AvatarUploader:

Call process on the version you would like to be cropped:

## If ONLY "thumb" version is to be cropped
version :jumbo do
  resize_to_limit(600,600)
end

version :thumb do
  process crop: :avatar  ## Crops this version based on original image
  resize_to_limit(100,100)
end

If there are no versions, and original file is to be cropped directly then call the process directly within AvatarUploader,

process crop: :avatar

##NOTES

1. Current Documentation is for CarrierWave-Crop v0.1.2

2. Supports processors rmagick and mini-magick.

   To use rmagick, add it in your Gemfile as:

    gem 'rmagick', :require => 'RMagick'  ## Specify appropriate version, if needed
   

   Run bundle

   Include it in your CarrierWave Uploader. For example:

    class AvatarUploader < CarrierWave::Uploader::Base
      include CarrierWave::RMagick
      ## ...
    end
   

   To use mini_magick, add it in your Gemfile as:

    gem 'mini_magick'  ## Specify appropriate version, if needed
   

   Run bundle

   Include it in your CarrierWave Uploader. For example:

    class AvatarUploader < CarrierWave::Uploader::Base
      include CarrierWave::MiniMagick
      ## ...
    end
   

3. Supports cropping of ONE attachment per model. Can be directly applied on original attachment if no versions exists.

    process crop: :avatar
   

4. Supports cropping of MULTIPLE versions of one attachment per model.

5. In form helpers, by default original image is rendered. To render a specific version for cropping pass version option. For example:

    <%= f.cropbox :avatar , version: :medium %>
    <%= f.previewbox :avatar , version: :medium %>  ## Pass the same version as specified in cropbox
   

6. By default previewbox has 100x100 dimensions and cropbox defaults to the target geometry for the version. width and height can be specified for these form helpers. BUT If you override ONE of width/height you MUST override both, otherwise passed option would be ignored.

    <%= f.cropbox :avatar, width: 550, height: 600 %>
    <%= f.previewbox :avatar, width: 200, height: 200 %>
   

7. By default, process crop: :avatar will create the cropped version based on original image. To resize the image to a particular dimension before cropping, pass two more arguments width and height.

    ## If ONLY "thumb" version is to be cropped
    version :jumbo do
      resize_to_limit(600,600)
    end
   
    version :thumb do
      ## To crop this version based on `jumbo` version, pass width = 600 and height = 600
      ## Specify both width and height values otherwise they would be ignored
      process crop: [:avatar, 600, 600]
      resize_to_limit(100,100)
    end
   

• CarrierWave
• Deep Liquid's JCrop
• And Ryan Bates Railscast#182