A lightweight and opinionated but hackable library for attaching images to ActiveRecord models.
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README.textile

HasImage

Image attachment gem/plugin for Ruby on Rails

HasImage allows Ruby on 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.

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

It is, by design, very simplistic: 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.

Another image attachment library? Why?

The three chief virtues of a programmer are: Laziness, Impatience and Hubris. – Larry Wall

Attachment_fu is too large and general for some of the places I want to use
images. I sometimes found myself writing more code to hack attachment_fu than
it took to create this gem. In fact, most of the code here has been plucked
from my various projects that use attachment_fu.

The other image attachment libraries I found fell short of my needs for
various other reasons, so I decided to roll my own.

HasImage vs. attachment_fu

Advantages

  • Simpler, smaller, more easily hackable codebase – and specialized for
    images only.
  • Installable via Ruby Gems. This makes version dependencies easy when using
    Rails 2.1.
  • Creates only one database record per image.
  • Has built-in facilities for making distortion-free, fixed-size thumbnails.
  • Doesn’t regenerate the thumbnails every time you save your model. This means
    you can easily use it, for example, inside a Member model to store member
    avatars.

Disadvantages

  • Doesn’t save image dimensions in the database. However, if you’re using
    fixed-sized images, you can read the size from MyModel.thumbnails[:my_size].
  • No support for AWS or DBFile storage, only filesystem.
  • Only supports MiniMagick as an image processor, no RMagick, GD, CoreImage, etc.
  • No support for anything other than image attachments.
  • Not as popular as attachment_fu, but then again if you use it you’ll be cooler (until HasImage becomes popular).

Examples

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

class Member < ActiveRecord::Base has_image end

Single image, no thumbnails, with some size limits:

class Picture < ActiveRecord::Base has_image :resize_to => “200×200”, :max_size => 3.megabytes, :min_size => 4.kilobytes end

Image with some thumbnails:

class Photo < ActiveRecord::Base has_image :resize_to => “640×480”, :thumbnails => { :square => “200×200”, :medium => “320×240” }, :max_size => 3.megabytes, :min_size => 4.kilobytes end

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 HasImage is simple, too:

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

Getting it

Has image can be installed as a gem, or as a Rails plugin. Gem installation
is easiest, and recommended:

gem install has_image

and add

require ‘has_image’

to your environment.rb file.

Alternatively, you can install it as a Rails plugin:

./script plugin install git://github.com/norman/has_image.git

Rails versions before 2.1 do not support plugin installation using Git, so if
you’re on 2.0 (or earlier), then please install the gem rather than the
plugin.

Then, make sure the model has a column named “has_image_file.”

Git repository: git://github.com/norman/has_image.git

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)
  1. your new-and-improved thumbnailer code goes here.
    end
    end
    end

HasImage 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.

My goal for HasImage is to keep it very small. If you need a lot of
functionality that’s not here, instead of patching this code, you will likely
be better off using attachment_fu, which is more powerful, but also more
complex.

Bugs

Please report them on Lighthouse.

Copyright © 2008 Norman Clarke, released under
the MIT license

Is anyone using this thing?

HasImage powers FotoBlog, one of the largest
Rails sites in Argentina. If you’re using it in your project let me know and
I’ll add your link here.

Acknowledgements

I’d like to thank the following contributors: