IIIF URL

Create and parse IIIF Image API URLs

Installation

Add this line to your application's Gemfile:

gem 'iiif_url'

And then execute:

$ bundle

Or install it yourself as:

$ gem install iiif_url

Usage

Here's the simplest case of creating a IIIF URL with all params. By default only the path is given without the scheme, server, port, or IIIF prefix.

iiif_base_url = "http://example.edu/prefix"
params = {
  identifier: 'abc',
  region: 'full',
  size: 'full',
  rotation: 0,
  quality: 'default',
  format: 'jpg'
}
url = IiifUrl.from_params(params)
# => "/abc/full/full/0/default.jpg"
full_url = File.join(iiif_base_url, url)
# => "http://example.edu/prefix/full/full/0/default.jpg"

If the base URL is set then it will form a full URL automatically:

IiifUrl.set_base_url("http://example.edu/prefix")
params = {
  identifier: 'abc',
  region: 'full',
  size: 'full',
  rotation: 0,
  quality: 'default',
  format: 'jpg'
}
url = IiifUrl.from_params(params)
# => "http://example.edu/prefix/abc/full/full/0/default.jpg"

You can also pass in the base URL in with the params, which will override any value set for the base URL.

IiifUrl.set_base_url("http://example.edu/prefix")
params = {
  identifier: 'abc',
  base_url: "http://example.org",
  region: 'full',
  size: 'full',
  rotation: 0,
  quality: 'default',
  format: 'jpg'
}
url = IiifUrl.from_params(params)
# => "http://example.org/abc/full/full/0/default.jpg"

If the base URL is set you can prevent it being used and just return the path portion by setting the base_url option key to false:

IiifUrl.set_base_url("http://example.edu/prefix")
params = {
  identifier: 'abc',
  base_url: false,
  region: 'full',
  size: 'full',
  rotation: 0,
  quality: 'default',
  format: 'jpg'
}
url = IiifUrl.from_params(params)
# => "/abc/full/full/0/default.jpg"

A more complicated region and size:

params = {
  identifier: 'abc',
  region: {
    x: 0,
    y: 0,
    w: 1000,
    h: 1200
  },
  size: {w: 300},
  rotation: 0,
  quality: 'default',
  format: 'jpg'
}
url = IiifUrl.from_params(params)
# => "/abc/0,0,1000,1200/300,/0/default.jpg"

To use a percent region or percent size, you must prefix the keys like this:

params = {
  identifier: 'abc',
  region: {
    pctx: 10,
    pcty: 10,
    pctw: 80,
    pcth: 80
  },
  size: {pct: 50}
}
url = IiifUrl.from_params(params)
# => "/abc/pct:10,10,80,80/pct:50/0/default.jpg"

If no identifier is passed in, then only the IIIF URL path will be returned:

params = {
  size: {pct: 50}
}
url = IiifUrl.from_params(params)
# => "/full/pct:50/0/default.jpg"

Even if a base_url is given if there is no identifier, then only the IIIF URL path will be returned:

params = {
  base_url: "http://example.org/prefix/",
  size: {pct: 50}
}
url = IiifUrl.from_params(params)
# => "/full/pct:50/0/default.jpg"

Defaults

You only need to specify values that are different from the defaults. The defaults are as specified:

parameter	value
identifier	null
region	"full"
size	"full"
rotation	"0"
quality	"default"
format	"jpg"

params = {
  identifier: 'abc',
  size: {w: 600}
}
url = IiifUrl.from_params(params)
# => "/abc/full/600,/0/default.jpg"

And without an identifier:

params = {
  size: {w: 600}
}
url = IiifUrl.from_params(params)
# => "/full/600,/0/default.jpg"

Chainable

There may be cases where you do not have all of the params you need so you want to pass around a IiifUrl to add more params.

url = IiifUrl.new
url.region({x:100, y:200, w: 300, h: 300})
url.size({w: 150}).format('png')
url.to_s
# => "/100,200,300,300/150,/0/default.png"

You can also pass in some initial params and then add on others:

url = IiifUrl.new({size: {w: 100}})
url.identifier('abc')
url.format('png')
url.rotation(180)
url.to_s
# => "/abc/full/100,/180/default.png"

Parser

IIIF URLs are parsed by segments including: region, size, rotation, quality, and format. The region and size segments can also be parsed into a string or hash. Rotation is always parsed into a hash. Quality and format are always a string.

Simple case for region and size parsed into strings:

params = IiifUrl.parse("/full/full/0/default.png")
# => {region: "full", size: "full", rotation: {degrees: 0, mirror: false}, quality: 'default', format: 'png'}

With an identifier:

params = IiifUrl.parse("/abc/full/full/0/default.png")
# => {identifier: "abc", region: "full", size: "full", rotation: {degrees: 0, mirror: false}, quality: 'default', format: 'png'}

Parameterized region and size:

params = IiifUrl.parse("/0,100,200,300/75,/0/default.jpg")
# => {identifier: nil, region: {x:0, y:100, w: 200, h: 300}, size: {w: 75, h: nil}, rotation: {degrees: 0, mirror: false}, quality: "default", format: "jpg" }

Parse a full URL:

params = IiifUrl.parse("http://example.org/prefix/abc/0,100,200,300/75,/0/default.jpg")
# => {identifier: abc, region: {x:0, y:100, w: 200, h: 300}, size: {w: 75, h: nil}, rotation: {degrees: 0, mirror: false}, quality: "default", format: "jpg" }

Validation

No validation is done for creating or parsing a URL. This allows for extensions to the IIIF Image API.

Development

After checking out the repo, run bin/setup to install dependencies. Then, run rake test to run the tests. You can also run bin/console for an interactive prompt that will allow you to experiment.

To install this gem onto your local machine, run bundle exec rake install. To release a new version, update the version number in version.rb, and then run bundle exec rake release, which will create a git tag for the version, push git commits and tags, and push the .gem file to rubygems.org.

Contributing

Bug reports and pull requests are welcome on GitHub at https://github.com/NCSU-Libraries/iiif_url.

Authors

Jason Ronallo

License

The gem is copyright North Carolina State University and is available as open source under the terms of the MIT License.