//The client side event Collapsed takes two parameters, sender and e.
//Sender is the object which is raising the event
//e is the SplitterCollapsedStateEventArgs
function WebImageViewer_ImageClick(sender, e) {
var imageviewer = $find("WebImageViewer1");
// Returns the ImageItem associated with the event
var imageItem = e.getImageItem();
// Gets the actual height of the image, not the height displayed in the
// browser
var imageHeight = imageItem.get_actualHeight();
// Gets the actual width of the image, not the width displayed in the
// browser
var imageWidth = imageItem.get_actualWidth();
// Get the index of the image item in the WebImageViewer's
// ImageItemCollection
var imageItemIndex = imageItem.get_index();
// Set the alt text of the image
imageItem.set_altText("Image Item "+imageItemIndex);
}