The Europeana Natural History Aggregator OpenUp! has developed scripts for the IIIF image conversion process that can be used to install a IIIF server and perform a IIIF image conversion. The scripts are available for download and reuse from a GitHub repository.
This guide describes in detail how image collection owners and their technical support may utilise the scripts to make their collections IIIF-compatible.
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1 Goal
IIIF stands for International Image Interoperability Framework (spoken Triple-Eye-F). The framework was created to offer the scientific community a way to productively interact with their digital objects (visual or audio/visual) and use them across different platforms. Here you can learn about the benefits of IIIF.
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The first two steps “Web server setup” and “Install the IIPImage Server” are described in detail in chapter 3 and 4 of this guide, but they can be easily executed automatically by running the script “iiif-install.sh” on your computer (find the script in chapter 9).
The step “Convert images to pyramid TIFFs”, described in chapter 5, can be carried out by running the “iiif-image-converter.sh” script (find the script in chapter 9).
2 Prior knowledge and technology
This guide is intended for people with basic prior knowledge of the Linux operating system (e.g. opening the terminal, basic Linux commands (https://opensource.com/article/22/5/essential-linux-commands ), difference between normal and sudo user, etc.). In addition, it would be good if you would familiarize yourself with the following points: IIIF and Image API (https://iiif.io/get-started/how-iiif-works/ ); multi-resolution image file formats (https://iipimage.sourceforge.io/documentation/images/ ).
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Operating system: Linux Debian, i.e. Ubuntu
sudo user with administration permissions
Webserver: Apache2
Image server: IIPImage Server
3 Web server setup
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Web servers are used to serve web pages requested by client computers. Apache is a widely used web server application. It is very secure, fast and reliable. It makes it possible to share your content (the offline web page) with other users in your network on a real website.
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Enter your IP address into your browser and if all goes well, your content will be loaded.
4 Install the IIPImage Server
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“The IIPImage Server is a feature-rich high performance image server engineered to be stable, fast and lightweight. It is designed for streaming extremely high resolution images and is capable of handling advanced image features such as 16 and 32 bit per channel depths, floating point data, CIELAB colorimetric images and scientific imagery such as multispectral or hyperspectral images and digital elevation map data.”
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If the start screen of the IIPImage server is shown then you are sure that the server configuration was successful and it runs correctly.
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5 Convert images to pyramid TIFFs
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With a multi-resolution format, large raster image files are compressed and can be quickly viewed without having to decompress the entire file. IIPImage Server supports multi-resolution images of the format TIFF and JEPG2000. Thus you need to convert your images to one of these types. In this guide we show how you can convert your images to TIFF format.
Figure 12 shows graphically how pyramid TIFFs are constructed. The Tiled Multi-Resolution (or Tiled Pyramidal) TIFF type allows the image server to enhance zoom options in a way that it switches to higher resolution images of the pyramid as the zoom goes deeper and deeper.
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Installation of the image processor VIPS
Before image transformation the installation of the image processor VIPS is necessary
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Now go to the folder where the original images are stored (e.g: cd /var/www/html/images/)
Image transformation
This is the main part of this chapter: image transformation.
If you have original images in .png format and you want to transform them into .tif then the following command is executed:
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In a final step, the script moves the converted images to the image servers’ data directory in order to make them accessible via the image server module.
6 Accessing Images in the Browser via a URL
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When you call an image via an IIPImage server URL, the image server will show you this image according to some parameters that you have set in the URL.
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The IIIF consortium provides a detailed documentation of the IIIF Image API’s parameters here.
7 Accessing Images in the Browser via the Manifest
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The Manifest is a container file (in the JSON format), that contains metadata about an image collection as well as the IIIF compliant URLs to the contained images.
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Using the manifest the images can be accessed and viewed with a IIIF-compliant image viewer like Mirador, Universal Viewer, OpenSeadragon etc.
Please see the IIIF Image Conversion Training for a detailed use case description.
8 Glossary
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Linux Debian i.e. Ubuntu | Ubuntu develops and maintains a cross-platform, open-source operating system based on Debian, with a focus on release quality, enterprise security updates and leadership in key platform capabilities for integration, security and usability. |
Apache | The Apache HTTP Server Project is an effort to develop and maintain an open-source HTTP server for modern operating systems including UNIX and Windows. |
IIPImage Server | The IIPImage server is a feature-rich high performance image server engineered to be stable, fast and lightweight. It is designed for streaming extremely high resolution images and is capable of handling advanced image features such as 16 and 32 bit per channel depths, floating point data, CIELAB colorimetric images and scientific imagery such as multispectral or hyperspectral images and digital elevation map data. |
Pyramid TIFF | Tiled Multi-Resolution (or Tiled Pyramidal) TIFF is simply a tiled multi-page TIFF image, with each resolution stored as a separate layer within the TIFF. |
libapache2-mod-fcgid | This package contains mod_fcgid, a high-performance alternative to mod_cgi or mod_cgid. It starts a sufficient number of instances of the CGI program to handle concurrent requests. These programs remain running to handle further incoming requests. |
IIIF | IIIF is a way to standardise the delivery of images and audio/visual files from servers to different environments on the Web where they can then be viewed and interacted with in many ways. |
IIIF Image API’s parameters | The IIIF Image API specifies a web service that returns an image in response to a standard HTTP or HTTPS request. The URI can specify the region, size, rotation, quality characteristics and format of the requested image. |
9 Scripts
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Access this GitHub repository to download the two scripts:
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