Created: 2008-07-18 13:40
Updated: 2017-12-05 15:50
License: mit


has_image - An Image attachment library for Active Record


The has_image library extends Active Record to allow Rails applications to have attached images. It is very small and lightweight: it only requires one column in your model to store the uploaded image's file name.

It was originally created as a smaller, simpler, lighter alternative to attachment_fu for applications that need to handle uploaded images.

It only supports using a filesystem for storage, and only supports MiniMagick as an image processor. However, its code is very small, clean and hackable, so adding support for other backends or processors should be fairly easy.

Some typical use cases are: websites that want to create photo galleries with fixed-dimension thumbnails, or that want to store user profile pictures without creating a separate model for the images.

It creates only one database record per image, and uses ImageMagick's crop and center gravity functions to produce thumbnails that generally look acceptable, unless the image is a panorama, or the subject matter is close to one of the margins, etc. For most sites where people upload pictures of themselves the generated thumbnails will look good almost all the time.


Point-and-drool use case. It's probably not what you want, but it may be useful for bootstrapping.

class Member < ActiveRecord::Base

Single image, no thumbnails, with some size limits:

class Picture < ActiveRecord::Base
  has_image :resize_to => "200x200",
    :max_size => 3.megabytes,
    :min_size => 4.kilobytes

Image with some thumbnails:

class Photo < ActiveRecord::Base
  has_image :resize_to => "640x480",
    :thumbnails => {
      :square => "200x200",
      :medium => "320x240"
    :max_size => 3.megabytes,
    :min_size => 4.kilobytes

It also provides a view helper to make displaying the images extremely simple:

<%= image_tag_for(@photo) # show the full-sized image %>
<%= image_tag_for(@photo, :thumb => :square) # show the square thumbnail %>

The image_tag_for helper calls Rails' image_tag, so you can pass in all the regular options to set the alt property, CSS class, etc:

<%= image_tag_for(@photo, :alt => "my cool picture", :class => "photo") %>

Setting up forms for has_image is simple, too:

<% form_for(@photo, :html => {:multipart => true}) do |f| %>
    <%= f.label :image_data %>
    <%= f.file_field :image_data %>
    <%= f.submit %>
<% end %>


Has_image is compatible with Rails 2.1.x - 3.0.x.

Getting it

Install has_image via RubyGems:

gem install has_image

and add it to your Gemfile (Rails 3.0.x) or environment.rb (Rails 2.x).

Then, add a column named has_image_file to your model.

API Docs


Source code



How do I validate the mime type of my uploaded images?

You don't. Rather than examine the mime type, has_image runs the "identify" command on the file to determine if it is processable by ImageMagick, and if it is, converts it to the format you specify, which defaults to JPEG.

This is better than checking for mime types, because your users may upload exotic image types that you didn't even realize would work, such as Truevision Targa images, or Seattle Film Works files.

If you wish to give users a list of file types they can upload, a good start would be jpeg, png, bmp, and maybe gif and ttf if your installation of ImageMagick understands them. You can find out what image types your ImageMagick understands by running:

identify -list format

Ideally, if your users just upload files that "look like" images on their computers, it has_image should "just work."

Hacking it

Don't like the way it makes images? Want to pipe the images through some crazy fast seam carving library written in OCaml, or watermark them with your corporate logo? Happiness is just a monkey-patch away:

module HasImage
  class Processor
    def resize_image(size)
      # your new-and-improved thumbnailer code goes here.

Has_image follows a philosophy of skinny model, fat plugin This means that it tries to pollute your ActiveRecord model with as little functionality as possible, so that in a sense, the model is acts like a "controller" and the plugin like a "model" as regards the image handling functionality. This makes it easier to test, hack, and reuse, because the storage and processing functionality is largely independent of your model, and of Rails.


Please report them on the Github issue tracker.

Copyright (c) 2008-2010 Norman Clarke and Adrian Mugnolo. Released under the MIT License.


We'd like to thank the following contributors for their help with has_image:

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