The Zoomify Image Viewer can display multiple Zoomify Images in layers for synchronized overlay viewing! One HTML parameter, zOverlayPath, is used to provide the path to an XML (text) file that includes the image paths for the one or more Zoomify Images to be used as overlays.
Overlays offer an alternative to simple hotspots or labels in that they apply actual zoomable image content. They also present an alternative when desiring to display a very large number of hotspots or labels. The Overlay feature differs from the Comparison feature in that the images are directly overlapping rather than side-by-side. And this differs from the Animation and Slidestack features in that the images can all be visible at one time.
Overlays can use standard Zoomify Images or Zoomify Images with transparency. Creating transparent overlays requires creating Zoomify Images with PNG tiles which simply requires changing settings within the Zoomify Unlimited Converter. See the Read Me First file in the Converter folder for step-by-step instructions.
Note that the base image path can be provided in the HTML as usual, or, if preferred, the image path can be null and the base image path can be provided as the first value in the overlays XML file. For more information, see the Parameter List document in the Documentation folder.
Also note that the Zoomify Image Viewer supports numerous functions that can be used to change overlays. For more information, see the next Overlay example and the Function List in the Documentation folder.
Satellite image courtesy GeoEye, Inc.