...Filter the images for viewing (should return true if the image is viewable, return false to ignore the image). Indicate if toggle the image size between its natural size and initial size when double click on the image or not. As there are some asynchronous processes when start the viewer, you should call a method only when it is available. If you have to use another viewer with the same namespace, call the Viewer.noConflict static method to revert to it.