wax:derivatives

There are two tasks namespaced under wax:derivatives, namely wax:derivatives:simple and wax:derivatives:iiif which represent the two options for generating collection image derivatives. You will only run one of these tasks per collection and you should only need to run it once.

wax:derivatives:simple

bundle exec rake wax:derivatives:simple YOUR_COLLECTION_NAME

When you run the line above for your collection, the task will:

  1. Look for the directory of source images you specified in your _config.yml file under collections > YOUR_COLLECTION_NAME > images > source (See: Updating your configuration)

  2. Generate two copies of each image (full size and thumbnail, with 1140px and 250px widths, respectively) into the directory img/derivatives/YOUR_COLLECTION_NAME

  3. Automatically add two fields (full and thumbnail) to each of your metadata records with the relative paths to the image derivatives.

(e.g., bundle exec rake wax:derivatives:simple qatar)

wax:derivatives:iiif

bundle exec rake wax:derivatives:iiif YOUR_COLLECTION_NAME

When you run the line above for your collection, the task will:

  1. Look for the directory of source images you specified in your _config.yml file under collections > YOUR_COLLECTION_NAME > images > source (See: Updating your configuration)

  2. Generate many IIIF derivatives, image tiles, and JSON representations of the collection items into the directory img/derivatives/YOUR_COLLECTION_NAME.

  3. Automatically add three fields (full, thumbnail, and manifest) to each of your metadata records with the relative paths to the full and thumbnail size image derivatives and the IIIF manifest.

(e.g., bundle exec rake wax:derivatives:iiif qatar)

Which one should I use?

Simple derivatives

Pros Cons
Fewer files to create, manage, and host Doesn’t handle items with multiple images / pdf format
Loads faster on webpages Lower quality images, no zooming
Users can copy/download full images Users can copy/download full images

IIIF derivatives

Pros Cons
Image content is interoperable, meaning it is standardized, (re)usable, and citable broadly (see: https://iiif.io/community/faq/#what-is-iiif) Slow to generate
Image content can leverage embedded metadata Slower to load on the page than simple derivatives
Can handle multiple images / paged content per collection item Requires the page to use a JS image viewer
Offers deep zooming of full images with no loss; Images are loaded quickly relative to the high resolution offered Higher technical overhead, more complex