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, magickly.afeld.me. 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:
- Blog post about how it's used at Jux
- Talk at Anatomy of a Ruby Gem (slides)
Installation
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.
flip=true
flop=true
glow=amount,softness
where amount is a float >= 1.0, and softness is an int >= 0.
greyscale=true
halftone=threshold
where threshold is a value between 0 and 100.
jcn=true
resize=geometry
rotate=degrees
saturation=percentage
percentage is the percentage of variation: a positive integer. 100 means no change. For example, to increase saturation by 50%, use saturation=150.
tilt_shift=true
thumb=geometry
(note: the %23 in the geometry string above is an encoded '#', which tells Dragonfly to fill the dimensions and crop)
two_color=true
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 (
?) withq/ - replace the ampersands (
&) and equals signs (=) with forward slashes (/) - make sure the
srcis encoded - this can be done in Javascript withencodeURIComponent()
Therefore, instead of
http://magickly.afeld.me/?src=http://upload.wikimedia.org/wikipedia/commons/thumb/0/0d/Imagemagick-logo.png/200px-Imagemagick-logo.png&thumb=200x100
the new URL would be
http://magickly.afeld.me/q/src/http%3A%2F%2Fupload.wikimedia.org%2Fwikipedia%2Fcommons%2Fthumb%2F0%2F0d%2FImagemagick-logo.png%2F200px-Imagemagick-logo.png/thumb/200x100
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
http://magickly.afeld.me/q/src/http%3A%2F%2Fupload.wikimedia.org%2Fwikipedia%2Fcommons%2Fthumb%2F0%2F0d%2FImagemagick-logo.png%2F200px-Imagemagick-logo.png/thumb/200x100
the new URL would be
http://magickly.afeld.me/qe/c3JjL2h0dHAlM0ElMkYlMkZ1cGxvYWQud2lraW1lZGlhLm9yZyUyRndpa2lwZWRpYSUyRmNvbW1vbnMlMkZ0aHVtYiUyRjAlMkYwZCUyRkltYWdlbWFnaWNrLWxvZ28ucG5nJTJGMjAwcHgtSW1hZ2VtYWdpY2stbG9nby5wbmcvdGh1bWIvMjAweDEwMA==
Analyzers
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:
magickly.afeld.me/analyze/number_of_colors?src=...
To get the list of available analyzers, visit magickly.afeld.me/analyze
Customization
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}"
end
end
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.
Disclaimer
The hosted version of the app (magickly.afeld.me) 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 :-)