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.

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. 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, 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.