The Comparison feature of the Zoomify Image Viewer displays two Viewports so that two images can be compared. The Comparison display can also include two image lists, one for each Viewport. These lists can be used to change the image displayed in either Viewport.

The optional value IMAGELIST is included in the comparison.xml file - not in the web page HTML. It is included in the XML twice, once for each IMAGE.

Note that changing the image displayed in one Viewport will cause the view in that Viewport to be reset to the initial X, Y, Zoom, and Rotation values for the new image as stated in the comparison.xml file. If the view coordinates are updated and the Sync checkbox in the Toolbar is checked, the other Viewport's coordinates will by sync'ed - even though its image is not being changed.

If, however, the Sync checkbox is not checked or if no values are provided for the new image in the comparison.xml file, the view coordinates will not be changed, but will be retained from the last state of the previously displayed image. This combination of behaviors allows the use of the XML and Sync checkbox to change images while updating and/or synchronizing the Viewport displays, as desired.

Note also that the width and height dimensions of all images to be compared must match or synchronization of the two Viewport displays will not be possible. Additional information is provided in the Parameter List.htm document in the documentation folder.