CarrierWave ↑

This gem provides a simple and extremely flexible way to upload files from Ruby applications. It works well with Rack based web applications, such as Ruby on Rails.

Information ↑

Getting Help ↑

Installation ↑

Install the latest release:

$ gem install carrierwave

In Rails, add it to your Gemfile:

gem 'carrierwave', '~> 3.0'

Finally, restart the server to apply the changes.

Upgrading from 2.x or earlier ↑

CarrierWave 3.0 comes with a change in the way of handling the file extension on conversion. This results in following issues if you use process convert: :format to change the file format:

To preserve the 2.x behavior, you can set force_extension false right after calling process convert: :format. See #2659 for the detail.

Getting Started ↑

Start off by generating an uploader:

    rails generate uploader Avatar

this should give you a file in:

    app/uploaders/avatar_uploader.rb

Check out this file for some hints on how you can customize your uploader. It should look something like this:

class AvatarUploader < CarrierWave::Uploader::Base
  storage :file
end

You can use your uploader class to store and retrieve files like this:

uploader = AvatarUploader.new

uploader.store!(my_file)

uploader.retrieve_from_store!('my_file.png')

CarrierWave gives you a store for permanent storage, and a cache for temporary storage. You can use different stores, including filesystem and cloud storage.

Most of the time you are going to want to use CarrierWave together with an ORM. It is quite simple to mount uploaders on columns in your model, so you can simply assign files and get going:

ActiveRecord ↑

Make sure you are loading CarrierWave after loading your ORM, otherwise you’ll need to require the relevant extension manually, e.g.:

require 'carrierwave/orm/activerecord'

Add a string column to the model you want to mount the uploader by creating a migration:

    rails g migration add_avatar_to_users avatar:string
    rails db:migrate

Open your model file and mount the uploader:

class User < ApplicationRecord
  mount_uploader :avatar, AvatarUploader
end

Now you can cache files by assigning them to the attribute, they will automatically be stored when the record is saved.

u = User.new
u.avatar = params[:file] # Assign a file like this, or

# like this
File.open('somewhere') do |f|
  u.avatar = f
end

u.save!
u.avatar.url # => '/url/to/file.png'
u.avatar.current_path # => 'path/to/file.png'
u.avatar_identifier # => 'file.png'

Note: u.avatar will never return nil, even if there is no photo associated to it. To check if a photo was saved to the model, use u.avatar.file.nil? instead.

DataMapper, Mongoid, Sequel ↑

Other ORM support has been extracted into separate gems:

There are more extensions listed in the wiki

Multiple file uploads ↑

CarrierWave also has convenient support for multiple file upload fields.

ActiveRecord ↑

Add a column which can store an array. This could be an array column or a JSON column for example. Your choice depends on what your database supports. For example, create a migration like this:

For databases with ActiveRecord json data type support (e.g. PostgreSQL, MySQL) ↑

    rails g migration add_avatars_to_users avatars:json
    rails db:migrate

For database without ActiveRecord json data type support (e.g. SQLite) ↑

    rails g migration add_avatars_to_users avatars:string
    rails db:migrate

Note: JSON datatype doesn’t exists in SQLite adapter, that’s why you can use a string datatype which will be serialized in model.

Open your model file and mount the uploader:

class User < ApplicationRecord
  mount_uploaders :avatars, AvatarUploader
  serialize :avatars, JSON # If you use SQLite, add this line.
end

Make sure that you mount the uploader with write (mount_uploaders) with s not (mount_uploader) in order to avoid errors when uploading multiple files

Make sure your file input fields are set up as multiple file fields. For example in Rails you’ll want to do something like this:

<%= form.file_field :avatars, multiple: true %>

Also, make sure your upload controller permits the multiple file upload attribute, pointing to an empty array in a hash. For example:

params.require(:user).permit(:email, :first_name, :last_name, {avatars: []})

Now you can select multiple files in the upload dialog (e.g. SHIFT+SELECT), and they will automatically be stored when the record is saved.

u = User.new(params[:user])
u.save!
u.avatars[0].url # => '/url/to/file.png'
u.avatars[0].current_path # => 'path/to/file.png'
u.avatars[0].identifier # => 'file.png'

If you want to preserve existing files on uploading new one, you can go like:

<% user.avatars.each do |avatar| %>
  <%= hidden_field :user, :avatars, multiple: true, value: avatar.identifier %>
<% end %>
<%= form.file_field :avatars, multiple: true %>

Sorting avatars is supported as well by reordering hidden_field, an example using jQuery UI Sortable is available here.

Changing the storage directory ↑

In order to change where uploaded files are put, just override the store_dir method:

class MyUploader < CarrierWave::Uploader::Base
  def store_dir
    'public/my/upload/directory'
  end
end

This works for the file storage as well as Amazon S3 and Rackspace Cloud Files. Define store_dir as nil if you’d like to store files at the root level.

If you store files outside the project root folder, you may want to define cache_dir in the same way:

class MyUploader < CarrierWave::Uploader::Base
  def cache_dir
    '/tmp/projectname-cache'
  end
end

Changing the filename ↑

To change the filename of uploaded files, you can override #filename method in the uploader.

class MyUploader < CarrierWave::Uploader::Base
  def filename
    "image.#{file.extension}" # If you upload 'file.jpg', you'll get 'image.jpg'
  end
end

Some old documentations (like this) may instruct you to safeguard the filename value with if original_filename, but it’s no longer necessary with CarrierWave 3.0 or later.

Securing uploads ↑

Certain files might be dangerous if uploaded to the wrong location, such as PHP files or other script files. CarrierWave allows you to specify an allowlist of allowed extensions or content types.

If you’re mounting the uploader, uploading a file with the wrong extension will make the record invalid instead. Otherwise, an error is raised.

class MyUploader < CarrierWave::Uploader::Base
  def extension_allowlist
    %w(jpg jpeg gif png)
  end
end

The same thing could be done using content types. Let’s say we need an uploader that accepts only images. This can be done like this

class MyUploader < CarrierWave::Uploader::Base
  def content_type_allowlist
    /image\//
  end
end

You can use a denylist to reject content types. Let’s say we need an uploader that reject JSON files. This can be done like this

class NoJsonUploader < CarrierWave::Uploader::Base
  def content_type_denylist
    ['application/text', 'application/json']
  end
end

CVE-2016-3714 (ImageTragick) ↑

This version of CarrierWave has the ability to mitigate CVE-2016-3714. However, you MUST set a content_type_allowlist in your uploaders for this protection to be effective, and you MUST either disable ImageMagick’s default SVG delegate or use the RSVG delegate for SVG processing.

A valid allowlist that will restrict your uploader to images only, and mitigate the CVE is:

class MyUploader < CarrierWave::Uploader::Base
  def content_type_allowlist
    [/image\//]
  end
end

WARNING: A content_type_allowlist is the only form of allowlist or denylist supported by CarrierWave that can effectively mitigate against CVE-2016-3714. Use of extension_allowlist will not inspect the file headers, and thus still leaves your application open to the vulnerability.

Filenames and unicode chars ↑

Another security issue you should care for is the file names (see Ruby On Rails Security Guide). By default, CarrierWave provides only English letters, arabic numerals and some symbols as allowlisted characters in the file name. If you want to support local scripts (Cyrillic letters, letters with diacritics and so on), you have to override sanitize_regexp method. It should return regular expression which would match all non-allowed symbols.

CarrierWave::SanitizedFile.sanitize_regexp = /[^[:word:]\.\-\+]/

Also make sure that allowing non-latin characters won’t cause a compatibility issue with a third-party plugins or client-side software.

Setting the content type ↑

As of v0.11.0, the mime-types gem is a runtime dependency and the content type is set automatically. You no longer need to do this manually.

Adding versions ↑

Often you’ll want to add different versions of the same file. The classic example is generating image thumbnails while preserving the original file to be used for high-quality representation. In this section we’ll explore how CarrierWave supports working with multiple versions. The image manipulation itself is covered in another section.

class MyUploader < CarrierWave::Uploader::Base
  include CarrierWave::MiniMagick

  process resize_to_fit: [800, 800]

  version :thumb do
    process resize_to_fill: [200,200]
  end

end

When this uploader is used, an uploaded image would be scaled to be no larger than 800 by 800 pixels. The original aspect ratio will be kept.

A version called :thumb is then created, which is scaled to exactly 200 by 200 pixels. The thumbnail uses resize_to_fill which makes sure that the width and height specified are filled, only cropping if the aspect ratio requires it.

The above uploader could be used like this:

uploader = AvatarUploader.new
uploader.store!(my_file)                              # size: 1024x768

uploader.url # => '/url/to/my_file.png'               # size: 800x800
uploader.thumb.url # => '/url/to/thumb_my_file.png'   # size: 200x200

One important thing to remember is that process is called before versions are created. This can cut down on processing cost.

Conditional processing ↑

If you want to use conditional process, you can only use if statement.

See carrierwave/uploader/processing.rb for details.

class MyUploader < CarrierWave::Uploader::Base
  process :scale => [200, 200], :if => :image?
  
  def image?(carrier_wave_sanitized_file)
    true
  end
end

Nested versions ↑

It is possible to nest versions within versions:

class MyUploader < CarrierWave::Uploader::Base

  version :animal do
    version :human
    version :monkey
    version :llama
  end
end

Conditional versions ↑

Occasionally you want to restrict the creation of versions on certain properties within the model or based on the picture itself.

class MyUploader < CarrierWave::Uploader::Base

  version :human, if: :is_human?
  version :monkey, if: :is_monkey?
  version :banner, if: :is_landscape?

private

  def is_human? picture
    model.can_program?(:ruby)
  end

  def is_monkey? picture
    model.favorite_food == 'banana'
  end

  def is_landscape? picture
    image = MiniMagick::Image.new(picture.path)
    image[:width] > image[:height]
  end

end

The model variable points to the instance object the uploader is attached to.

Create versions from existing versions ↑

For performance reasons, it is often useful to create versions from existing ones instead of using the original file. If your uploader generates several versions where the next is smaller than the last, it will take less time to generate from a smaller, already processed image.

class MyUploader < CarrierWave::Uploader::Base

  version :thumb do
    process resize_to_fill: [280, 280]
  end

  version :small_thumb, from_version: :thumb do
    process resize_to_fill: [20, 20]
  end

end

Customizing version filenames ↑

CarrierWave supports customization of filename by overriding an uploader’s

filename method, but this doesn’t work for versions because of the limitation on how CarrierWave ↑

re-constructs the filename on retrieval of the stored file. Instead, you can override #full_filename with providing a version-aware name.

class MyUploader < CarrierWave::Uploader::Base
  version :thumb do
    def full_filename(for_file)
      'thumb.png'
    end
    process convert: 'png'
  end
end

Please note that #full_filename mustn’t be constructed based on a dynamic value that can change from the time of store and time of retrieval, since it will result in being unable to retrieve a file previously stored.

Making uploads work across form redisplays ↑

Often you’ll notice that uploaded files disappear when a validation fails. CarrierWave has a feature that makes it easy to remember the uploaded file even in that case. Suppose your user model has an uploader mounted on avatar file, just add a hidden field called avatar_cache (don’t forget to add it to the attr_accessible list as necessary). In Rails, this would look like this:

<%= form_for @user, html: { multipart: true } do |f| %>
  <p>
    <label>My Avatar</label>
    <%= f.file_field :avatar %>
    <%= f.hidden_field :avatar_cache %>
  </p>
<% end %>
````

It might be a good idea to show the user that a file has been uploaded, in the
case of images, a small thumbnail would be a good indicator:

erb <%= form_for @user, html: { multipart: true } do |f| %> <p> <label>My Avatar</label> <%= image_tag(@user.avatar_url) if @user.avatar? %> <%= f.file_field :avatar %> <%= f.hidden_field :avatar_cache %> </p> <% end %>

## Removing uploaded files

If you want to remove a previously uploaded file on a mounted uploader, you can
easily add a checkbox to the form which will remove the file when checked.

erb <%= form_for @user, html: { multipart: true } do |f| %> <p> <label>My Avatar</label> <%= image_tag(@user.avatar_url) if @user.avatar? %> <%= f.file_field :avatar %> </p>

<p> <label> <%= f.check_box :remove_avatar %> Remove avatar </label> </p> <% end %>

If you want to remove the file manually, you can call <code>remove_avatar!</code>, then save the object.

erb @user.remove_avatar! @user.save

=> true ↑

## Uploading files from a remote location

Your users may find it convenient to upload a file from a location on the Internet
via a URL. CarrierWave makes this simple, just add the appropriate attribute to your
form and you're good to go:

erb <%= form_for @user, html: { multipart: true } do |f| %> <p> <label>My Avatar URL:</label> <%= image_tag(@user.avatar_url) if @user.avatar? %> <%= f.text_field :remote_avatar_url %> </p> <% end %>

If you're using ActiveRecord, CarrierWave will indicate invalid URLs and download
failures automatically with attribute validation errors. If you aren't, or you
disable CarrierWave's `validate_download` option, you'll need to handle those
errors yourself.

### Retry option for download from remote location
If you want to retry the download from the Remote URL, enable the download_retry_count option, an error occurs during download, it will try to execute the specified number of times.
This option is effective when the remote destination is unstable.

rb CarrierWave.configure do |config| config.download_retry_count = 3 # Default 0 config.download_retry_wait_time = 3 # Default 5 end

## Providing a default URL

In many cases, especially when working with images, it might be a good idea to
provide a default url, a fallback in case no file has been uploaded. You can do
this easily by overriding the `default_url` method in your uploader:

ruby class MyUploader < CarrierWave::Uploader::Base def default_url(*args) “/images/fallback/” + [version_name, “default.png”].compact.join(‘_’) end end

Or if you are using the Rails asset pipeline:

ruby class MyUploader < CarrierWave::Uploader::Base def default_url(*args) ActionController::Base.helpers.asset_path(“fallback/” + [version_name, “default.png”].compact.join(‘_’)) end end

## Recreating versions

You might come to a situation where you want to retroactively change a version
or add a new one. You can use the `recreate_versions!` method to recreate the
versions from the base file. This uses a naive approach which will re-upload and
process the specified version or all versions, if none is passed as an argument.

When you are generating random unique filenames you have to call `save!` on
the model after using `recreate_versions!`. This is necessary because
`recreate_versions!` doesn't save the new filename to the database. Calling
`save!` yourself will prevent that the database and file system are running
out of sync.

ruby instance = MyUploader.new instance.recreate_versions!(:thumb, :large)

Or on a mounted uploader:

ruby User.find_each do |user| user.avatar.recreate_versions! end

Note: `recreate_versions!` will throw an exception on records without an image. To avoid this, scope the records to those with images or check if an image exists within the block. If you're using ActiveRecord, recreating versions for a user avatar might look like this:

ruby User.find_each do |user| user.avatar.recreate_versions! if user.avatar? end

## Configuring CarrierWave

CarrierWave has a broad range of configuration options, which you can configure,
both globally and on a per-uploader basis:

ruby CarrierWave.configure do |config| config.permissions = 0666 config.directory_permissions = 0777 config.storage = :file end

Or alternatively:

ruby class AvatarUploader < CarrierWave::Uploader::Base permissions 0777 end

If you're using Rails, create an initializer for this:

        config/initializers/carrierwave.rb

If you want CarrierWave to fail noisily in development, you can change these configs in your environment file:

ruby CarrierWave.configure do |config| config.ignore_integrity_errors = false config.ignore_processing_errors = false config.ignore_download_errors = false end


## Testing with CarrierWave

It's a good idea to test your uploaders in isolation. In order to speed up your
tests, it's recommended to switch off processing in your tests, and to use the
file storage. In Rails you could do that by adding an initializer with:

ruby if Rails.env.test? or Rails.env.cucumber? CarrierWave.configure do |config| config.storage = :file config.enable_processing = false end end

Remember, if you have already set `storage :something` in your uploader, the `storage`
setting from this initializer will be ignored.

If you need to test your processing, you should test it in isolation, and enable
processing only for those tests that need it.

CarrierWave comes with some RSpec matchers which you may find useful:

ruby require ‘carrierwave/test/matchers’

describe MyUploader do include CarrierWave::Test::Matchers

let(:user) { double(‘user’) } let(:uploader) { MyUploader.new(user, :avatar) }

before do MyUploader.enable_processing = true File.open(path_to_file) { |f| uploader.store!(f) } end

after do MyUploader.enable_processing = false uploader.remove! end

context ‘the thumb version’ do it “scales down a landscape image to be exactly 64 by 64 pixels” do expect(uploader.thumb).to have_dimensions(64, 64) end end

context ‘the small version’ do it “scales down a landscape image to fit within 200 by 200 pixels” do expect(uploader.small).to be_no_larger_than(200, 200) end end

it “makes the image readable only to the owner and not executable” do expect(uploader).to have_permissions(0600) end

it “has the correct format” do expect(uploader).to be_format(‘png’) end end

If you're looking for minitest asserts, checkout [carrierwave_asserts](https://github.com/hcfairbanks/carrierwave_asserts).

Setting the enable_processing flag on an uploader will prevent any of the versions from processing as well.
Processing can be enabled for a single version by setting the processing flag on the version like so:

ruby @uploader.thumb.enable_processing = true

## Fog

If you want to use fog you must add in your CarrierWave initializer the
following lines

ruby config.fog_credentials = { … } # Provider specific credentials

## Using Amazon S3

[Fog AWS](http://github.com/fog/fog-aws) is used to support Amazon S3. Ensure you have it in your Gemfile:

ruby gem “fog-aws”

You'll need to provide your fog_credentials and a fog_directory (also known as a bucket) in an initializer.
For the sake of performance it is assumed that the directory already exists, so please create it if it needs to be.
You can also pass in additional options, as documented fully in lib/carrierwave/storage/fog.rb. Here's a full example:

ruby CarrierWave.configure do |config| config.fog_credentials = { provider: ‘AWS’, # required aws_access_key_id: ‘xxx’, # required unless using use_iam_profile aws_secret_access_key: ‘yyy’, # required unless using use_iam_profile use_iam_profile: true, # optional, defaults to false region: ‘eu-west-1’, # optional, defaults to ‘us-east-1’ host: ‘s3.example.com’, # optional, defaults to nil endpoint: ‘s3.example.com:8080’ # optional, defaults to nil } config.fog_directory = ‘name_of_bucket’ # required config.fog_public = false # optional, defaults to true config.fog_attributes = { cache_control: “public, max-age=#{365.days.to_i}” } # optional, defaults to {} # For an application which utilizes multiple servers but does not need caches persisted across requests, # uncomment the line :file instead of the default :storage. Otherwise, it will use AWS as the temp cache store. # config.cache_storage = :file end

In your uploader, set the storage to :fog

ruby class AvatarUploader < CarrierWave::Uploader::Base storage :fog end

That's it! You can still use the `CarrierWave::Uploader#url` method to return the url to the file on Amazon S3.

**Note**: for Carrierwave to work properly it needs credentials with the following permissions:

* `s3:ListBucket`
* `s3:PutObject`
* `s3:GetObject`
* `s3:DeleteObject`
* `s3:PutObjectAcl`

## Using Rackspace Cloud Files

[Fog](http://github.com/fog/fog) is used to support Rackspace Cloud Files. Ensure you have it in your Gemfile:

ruby gem “fog”

You'll need to configure a directory (also known as a container), username and API key in the initializer.
For the sake of performance it is assumed that the directory already exists, so please create it if need be.

Using a US-based account:

ruby CarrierWave.configure do |config| config.fog_credentials = { provider: ‘Rackspace’, rackspace_username: ‘xxxxxx’, rackspace_api_key: ‘yyyyyy’, rackspace_region: :ord # optional, defaults to :dfw } config.fog_directory = ‘name_of_directory’ end

Using a UK-based account:

ruby CarrierWave.configure do |config| config.fog_credentials = { provider: ‘Rackspace’, rackspace_username: ‘xxxxxx’, rackspace_api_key: ‘yyyyyy’, rackspace_auth_url: Fog::Rackspace::UK_AUTH_ENDPOINT, rackspace_region: :lon } config.fog_directory = ‘name_of_directory’ end

You can optionally include your CDN host name in the configuration.
This is *highly* recommended, as without it every request requires a lookup
of this information.

ruby config.asset_host = “c000000.cdn.rackspacecloud.com”

In your uploader, set the storage to :fog

ruby class AvatarUploader < CarrierWave::Uploader::Base storage :fog end

That's it! You can still use the `CarrierWave::Uploader#url` method to return
the url to the file on Rackspace Cloud Files.

## Using Google Cloud Storage

[Fog](http://github.com/fog/fog-google) is used to support Google Cloud Storage. Ensure you have it in your Gemfile:

ruby gem “fog-google”

You'll need to configure a directory (also known as a bucket) and the credentials in the initializer.
For the sake of performance it is assumed that the directory already exists, so please create it if need be.

Please read the [fog-google README](https://github.com/fog/fog-google/blob/master/README.md) on how to get credentials.

For Google Storage JSON API (recommended):

ruby CarrierWave.configure do |config| config.fog_credentials = { provider: ‘Google’, google_project: ‘my-project’, google_json_key_string: ‘xxxxxx’ # or use google_json_key_location if using an actual file } config.fog_directory = ‘google_cloud_storage_bucket_name’ end

For Google Storage XML API:

ruby CarrierWave.configure do |config| config.fog_credentials = { provider: ‘Google’, google_storage_access_key_id: ‘xxxxxx’, google_storage_secret_access_key: ‘yyyyyy’ } config.fog_directory = ‘google_cloud_storage_bucket_name’ end

In your uploader, set the storage to :fog

ruby class AvatarUploader < CarrierWave::Uploader::Base storage :fog end

That's it! You can still use the `CarrierWave::Uploader#url` method to return
the url to the file on Google.

## Optimized Loading of Fog

Since Carrierwave doesn't know which parts of Fog you intend to use, it will just load the entire library (unless you use e.g. [`fog-aws`, `fog-google`] instead of fog proper). If you prefer to load fewer classes into your application, you need to load those parts of Fog yourself *before* loading CarrierWave in your Gemfile.  Ex:

ruby gem “fog”, “~> 1.27”, require: “fog/rackspace/storage” gem “carrierwave”

A couple of notes about versions:
* This functionality was introduced in Fog v1.20.
* This functionality is slated for CarrierWave v1.0.0.

If you're not relying on Gemfile entries alone and are requiring "carrierwave" anywhere, ensure you require "fog/rackspace/storage" before it.  Ex:

ruby require “fog/rackspace/storage” require “carrierwave”

Beware that this specific require is only needed when working with a fog provider that was not extracted to its own gem yet.
A list of the extracted providers can be found in the page of the `fog` organizations [here](https://github.com/fog).

When in doubt, inspect `Fog.constants` to see what has been loaded.

## Dynamic Asset Host

The `asset_host` config property can be assigned a proc (or anything that responds to `call`) for generating the host dynamically. The proc-compliant object gets an instance of the current `CarrierWave::Storage::Fog::File` or `CarrierWave::SanitizedFile` as its only argument.

ruby CarrierWave.configure do |config| config.asset_host = proc do |file| identifier = # some logic “http://#{identifier}.cdn.rackspacecloud.com” end end

## Manipulating images

If you're uploading images, you'll probably want to manipulate them in some way,
you might want to create thumbnail images for example.

### Using MiniMagick

MiniMagick performs all the operations using the 'convert' CLI which is part of the standard ImageMagick kit.
This allows you to have the power of ImageMagick without having to worry about installing
all the RMagick libraries, it often results in higher memory footprint.

See the MiniMagick site for more details:

https://github.com/minimagick/minimagick

To install Imagemagick on OSX with homebrew type the following:

$ brew install imagemagick

And the ImageMagick command line options for more for what's on offer:

http://www.imagemagick.org/script/command-line-options.php

Currently, the MiniMagick carrierwave processor provides exactly the same methods as
for the RMagick processor.

ruby class AvatarUploader < CarrierWave::Uploader::Base include CarrierWave::MiniMagick

process resize_to_fill: [200, 200] end

#### List of available processing methods:

- `convert` - Changes the image encoding format to the given format(eg. jpg). This operation is treated specially to trigger the change of the file extension, so it matches with the format of the resulting file.
- `resize_to_limit` - Resize the image to fit within the specified dimensions while retaining the original aspect ratio. Will only resize the image if it is larger than the specified dimensions. The resulting image may be shorter or narrower than specified in the smaller dimension but will not be larger than the specified values.
- `resize_to_fit` - Resize the image to fit within the specified dimensions while retaining the original aspect ratio. The image may be shorter or narrower than specified in the smaller dimension but will not be larger than the specified values.
- `resize_to_fill` - Resize the image to fit within the specified dimensions while retaining the aspect ratio of the original image. If necessary, crop the image in the larger dimension. Optionally, a "gravity" may be specified, for example "Center", or "NorthEast".
- `resize_and_pad` - Resize the image to fit within the specified dimensions while retaining the original aspect ratio. If necessary, will pad the remaining area with the given color, which defaults to transparent (for gif and png, white for jpeg). Optionally, a "gravity" may be specified, as above.

See `carrierwave/processing/mini_magick.rb` for details.

### Using RMagick

CarrierWave also comes with support for RMagick, a well-known image processing library.
To use it, you'll need to include this in your Uploader:

ruby class AvatarUploader < CarrierWave::Uploader::Base include CarrierWave::RMagick end

The RMagick module gives you a few methods, like
`CarrierWave::RMagick#resize_to_fill` which manipulate the image file in some
way. You can set a `process` callback, which will call that method any time a
file is uploaded.
There is a demonstration of convert here.

ruby class AvatarUploader < CarrierWave::Uploader::Base include CarrierWave::RMagick

process resize_to_fill: [200, 200] process convert: ‘png’ end

Check out the manipulate! method, which makes it easy for you to write your own
manipulation methods.

## Migrating from Paperclip

If you are using Paperclip, you can use the provided compatibility module:

ruby class AvatarUploader < CarrierWave::Uploader::Base include CarrierWave::Compatibility::Paperclip end

See the documentation for `CarrierWave::Compatibility::Paperclip` for more
details.

Be sure to use mount_on to specify the correct column:

ruby mount_uploader :avatar, AvatarUploader, mount_on: :avatar_file_name

## I18n

The Active Record validations use the Rails `i18n` framework. Add these keys to
your translations file:

yaml errors: messages: carrierwave_processing_error: failed to be processed carrierwave_integrity_error: is not of an allowed file type carrierwave_download_error: could not be downloaded extension_allowlist_error: “You are not allowed to upload %{extension} files, allowed types: %{allowed_types}” extension_denylist_error: “You are not allowed to upload %{extension} files, prohibited types: %{prohibited_types}” content_type_allowlist_error: “You are not allowed to upload %{content_type} files, allowed types: %{allowed_types}” content_type_denylist_error: “You are not allowed to upload %{content_type} files” processing_error: “Failed to manipulate, maybe it is not an image?” min_size_error: “File size should be greater than %{min_size}” max_size_error: “File size should be less than %{max_size}” min_width_error: “Image width should be greater than %{min_width}px” max_width_error: “Image width should be less than %{max_width}px” min_height_error: “Image height should be greater than %{min_height}px” max_height_error: “Image height should be less than %{max_height}px”

The [`carrierwave-i18n`](https://github.com/carrierwaveuploader/carrierwave-i18n)
library adds support for additional locales.

## Large files

By default, CarrierWave copies an uploaded file twice, first copying the file into the cache, then
copying the file into the store.  For large files, this can be prohibitively time consuming.

You may change this behavior by overriding either or both of the `move_to_cache` and
`move_to_store` methods:

ruby class MyUploader < CarrierWave::Uploader::Base def move_to_cache true end

def move_to_store true end end

When the `move_to_cache` and/or `move_to_store` methods return true, files will be moved (instead of copied) to the cache and store respectively.

This has only been tested with the local filesystem store.

## Skipping ActiveRecord callbacks

By default, mounting an uploader into an ActiveRecord model will add a few
callbacks. For example, this code:

ruby class User mount_uploader :avatar, AvatarUploader end

Will add these callbacks:

ruby before_save :write_avatar_identifier after_save :store_previous_changes_for_avatar after_commit :remove_avatar!, on: :destroy after_commit :mark_remove_avatar_false, on: :update after_commit :remove_previously_stored_avatar, on: :update after_commit :store_avatar!, on: [:create, :update]

If you want to skip any of these callbacks (eg. you want to keep the existing
avatar, even after uploading a new one), you can use ActiveRecord’s
`skip_callback` method.

ruby class User mount_uploader :avatar, AvatarUploader skip_callback :commit, :after, :remove_previously_stored_avatar end

## Uploader Callbacks

In addition to the ActiveRecord callbacks described above, uploaders also have callbacks.

ruby class MyUploader < ::CarrierWave::Uploader::Base before :remove, :log_removal private def log_removal ::Rails.logger.info(format(‘Deleting file on S3: %s’, @file)) end end

Uploader callbacks can be `before` or `after` the following events:

cache process remove retrieve_from_cache store

“‘

Contributing to CarrierWave ↑

See CONTRIBUTING.md

License ↑

The MIT License (MIT)

Copyright © 2008 Jonas Nicklas

Permission is hereby granted, free of charge, to any person obtaining a copy of this software and associated documentation files (the “Software”), to deal in the Software without restriction, including without limitation the rights to use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the Software, and to permit persons to whom the Software is furnished to do so, subject to the following conditions:

The above copyright notice and this permission notice shall be included in all copies or substantial portions of the Software.

THE SOFTWARE IS PROVIDED “AS IS”, WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.