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Omeka plugin that provides an OpenSeadragon zoomable image viewer
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README.md

OpenSeadragon plugin for Omeka

This is a plugin for Omeka 2.x that adds an zoomable image viewer provided by OpenSeadragon, usable on item pages, exhibits, and the Omeka admin dashboard.

This plugin was originally based on the ZoomIt plugin for Omeka, and the fork of that plugin used in the DPLA Exhibitions codebase.

Requirements

  • Omeka 2.0 or higher
  • The gd (recommended) and/or the exif modules for PHP

How it works

Omeka uses ImageMagick to generate derivatives of any image added. For example, if you have an high resolution JPEG image, it will treat that image as the "original", and derive "fullsize" (medium resolution) images and thumbnails automatically.

The OpenSeadragon plugin uses OpenSeadragon's support for "legacy image pyramids" to pull in those original, fullsize, and thumbnail images from Omeka. Since OpenSeadragon requires the image size to be stated explicitly for images in any image pyramid, we need to obtain the dimensions from each of the files, either through metadata stored in the Omeka database for each file, or through using either gd or exif functions.

Known issues:

Only works with original images in formats supported by OpenSeadragon's LegacyTileSource class (JPEG, GIF, and PNG). Specifically, this impacts you if you're using high resolution images in TIFF or JPEG 2000 (JP2) format. If you want to load high resolution versions of these, you'll need to convert them to a supported format or only rely on the fullsize and thumbnail sizes.

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