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Rodent-Assimilated Image Server

Gocutus, the RAIS mascot

RAIS was originally built by eikeon as a 100% open source, no-commercial-products-required, proof-of-concept tile server for JP2 images within chronam.

It has been updated to allow more command-line options, more source file formats, more features, and conformance to the IIIF spec.

RAIS is very efficient, completely free, and easy to set up and run. See our wiki pages for more details and documentation.


Main Configuration Settings

RAIS uses a configuration system that allows environment variables, a config file, and/or command-line flags. See rais-example.toml for an example of a configuration file. RAIS will use a configuration file if one exists at /etc/rais.toml.

The configuration file's values can be overridden by environment variables, while command-line flags will override both configuration files and environmental variables. Configuration is best explained and understood by reading the example file above, which describes all the values in detail.

Cloud Settings

Because connecting to a cloud provider is optional, often means using a container-based setup, and differs from one provider to the next, all RAIS cloud configuration is environment-only. This means it can't be specified on the command line or in rais.toml.

Currently RAIS can theoretically support S3, Azure, and Google Cloud backends, but only S3 has had much testing. To set up RAIS for S3, you would have to export the following environment variables (in addition to having an S3-compatible object store running):

  • AWS_ACCESS_KEY_ID: Required
  • AWS_REGION: Required
  • RAIS_S3_ENDPOINT: optionally set for custom S3 backends; e.g., "minio:9000"
  • RAIS_S3_DISABLESSL: optionally set this to "true" for custom S3 backends which don't need SSL (for instance if they're running on the same server as RAIS)
  • RAIS_S3_FORCEPATHSTYLE: optionally set this to "true" to force path-style S3 calls. This is typically necessary for custom S3 backends like minio, but not for AWS.

Other backends have their own environment variables which have to be set in order to have RAIS connect to them.

For a full demo of a working custom S3 backend powered by minio, see docker/s3demo.

Note that external storage is going to be slower than serving images from local filesystems! Make sure you test carefully!

IIIF Features

RAIS supports level 2 of the IIIF Image API 2.1 as well as a handful of features beyond level 2. See the IIIF Features wiki page for an in-depth look at feature support.


RAIS can internally cache the IIIF info.json requests and individual tile requests. See the RAIS Caching wiki page for details.

Generating tiled, multi-resolution JP2s

RAIS performs best with JP2s which are generated as tiled, multi-resolution (think "zoom levels") images. Generating images like this is fairly easy with either the openjpeg tools or graphicsmagick. Other tools probably do this well, but we've only directly used those.

You can find detailed instructions on the How to encode jp2s wiki page.



RAIS Image Server is in the public domain under a CC0 license.


Special thanks to Jessica Dussault (@jduss4) for providing the hand-drawn "Gocutus" logo, and Greg Tunink (@techgique) for various digital refinements to said logo.