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image manipulation as a (plugin-able) service
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Magickly - image manipulation as a (plugin-able) service

Built as a practical wrapper of Imagemagick which handles caching, c/o the Dragonfly gem.

Say the base URL is the hosted version of this app, The image URL is appended to the query string as a src=, followed by any of the supported operations below. Multiple operations can be combined, and will be applied in order.

If no query params are provided, a simple sandbox page is displayed. Try it here:

More insights:


Compatible with Ruby 1.9.3, 2.0 and 2.1, and jRuby (in 1.9 mode). Requires Imagemagick >= v6.2.4.

$ gem install magickly

Running the App

A few options:

A. Run the app directly

# in the app directory:
$ gem install thin
$ thin start

The app can be accessed at http://localhost:3000.

When running as an app, Rack::Cache is used to cache generated versions of images. These cached files and metadata are stored in the tmp/ directory and will get regenerated as necessary.

B. Use as an endpoint in another Rack app

As an example, to have magickly accessible at /magickly in a Rails app:

# Gemfile
gem 'magickly', '~> 1.1'

# config/routes.rb
match '/magickly', :to => Magickly::App, :anchor => false

For more info, see Rails Routing from the Outside In or Michael Raidel's Mount Rails apps in Rails 3.

Processing Parameters

See the Dragonfly documentation for more details about the permitted geometry values.

src=url (required)

The URL of the original image.

brightness_contrast=br. x con.

brightness and contrast are percentage change, between -100 and 100. For example, to increase contrast by 20% but leave brightness unchanged, use brightness_contrast=0x20.

tanned imagemagick logo


flipped imagemagick logo


flopped imagemagick logo


where amount is a float >= 1.0, and softness is an int >= 0.

glowing imagemagick logo,20


flopped imagemagick logo


where threshold is a value between 0 and 100.

halftone imagemagick logo


JCN imagemagick logo


resized imagemagick logo


rotated imagemagick logo


percentage is the percentage of variation: a positive integer. 100 means no change. For example, to increase saturation by 50%, use saturation=150.

saturated imagemagick logo


tilt-shifted imagemagick logo


thumbnail of imagemagick logo

(note: the %23 in the geometry string above is an encoded '#', which tells Dragonfly to fill the dimensions and crop)


two color imagemagick logo

Alternate Syntax

Some CDNs are jerks and don't respect query params on resources (ahem CLOUDFRONT ahem) when caching. To use this syntax:

  • replace the question mark that starts the query string (?) with q/
  • replace the ampersands (&) and equals signs (=) with forward slashes (/)
  • make sure the src is encoded - this can be done in Javascript with encodeURIComponent()

Therefore, instead of

the new URL would be

Encoded Syntax

Sometimes, you just can't handle escaped entities in your URLs (Facebook's handling of OpenGraph tags, for example). In those cases, we provide a Base64 encoded syntax which is an extension of the path-based Alternate Syntax above. Once your path-based url is constructed (see "Alternate Syntax" above), simply pass everything after the q/ through Base64.urlsafe_encode or the javascript btoa() function and send it to the qe/ endpoint instead.

Therefore, instead of

the new URL would be


Magickly v1.2.0 introduces the ability to retrieve image properties via a REST API. For example, to retrieve the number of colors in the photo, visit:

To get the list of available analyzers, visit


In addition to the available parameters listed above, custom "shortcuts" can be created to perform arbitrary imagemagick operations. For example, to create a shortcut called resize_with_blur:

# somewhere in your app configuration, i.e. config/initializers/magickly.rb for a Rails 3 app
Magickly.dragonfly.configure do |c|
  c.job :resize_with_blur do |size|
    process :convert, "-filter Gaussian -resize #{size}"

which can then be used with the query string ?src=...&resize_with_blur=200x. Note that magickly will pass the value of the query param to the block as a single string.

See the Dragonfly documentation for more info on "shortcuts", and the shortcuts.rb file for examples.


The hosted version of the app ( is a single app instance intended for demonstration purposes - if you are going to be making a large number of API calls to it or would like to use it in production, please let us know :-)

See Also

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