Image Viewer in Single Item Mode

ImageViewer supports any number of items with multiple view layouts. However, some applications simply want to use the viewer with a single image and do not want to deal with setting up the layouts or dealing with the item collection. For these types of applications, ImageViewer offers the single item mode.

As described in Image Viewer Items, if there are items in the viewer, one of them is donated as the active item and from Image Viewer Layouts, the viewer supports the ImageViewerSingleViewLayout that displays a single item at the item - the active item. Therefore it is easy to setup the viewer to display a single item all the time:

// Create a single view layout 
var layout = new ImageViewerSingleViewLayout(); 
// Create the viewer, passing this layout 
var imageViewer = new ImageViewer(layout); 
// Add an empty item 
var item = new ImageViewerItem(); 
imageViewer.Items.Add(item); 
// Now, ImageViewer.ActiveItem is item 

This is exactly what the default constructor of ImageViewer does:

var imageViewer = new ImageViewer();

After the viewer is setup like this, it is easy to forget about the view layout and the items collection and just use the ActiveItem property to view images. Set an image into the viewer:

imageViewer.ActiveItem.Image = myImage;

Or to remove the image:

imageViewer.ActiveItem.Image = null;

To get its transform:

var transform = imageViewer.GetItemImageTransform(imageViewer.ActiveItem);

Or to convert a point from image to control coordinate and back:

controlPoint = imageViewer.ConvertPoint(imageViewer.ActiveItem, ImageViewerCoordinateType.Image, ImageViewerCoordinateType.Control, imagePoint); 
imagePoint = imageViewer.ConvertPoint(imageViewer.ActiveItem, ImageViewerCoordinateType.Control, ImageViewerCoordinateType.Image, controlPoint); 

In addition to using the ActiveItem property, the viewer also contains shortcut methods and properties that can be used in single item mode. The following is the same code as above using these shortcuts. Set an image into the viewer:

imageViewer.Image = myImage;

Or to remove the image:

imageViewer.Image = null;

To get its transform:

var transform = imageViewer.ImageTransform;

Or to convert a point from image to control coordinate and back:

controlPoint = imageViewer.ConvertPoint(null, ImageViewerCoordinateType.Image, ImageViewerCoordinateType.Control, imagePoint); 
imagePoint = imageViewer.ConvertPoint(null, ImageViewerCoordinateType.Control, ImageViewerCoordinateType.Image, controlPoint); 

With these properties/methods, you can use the ImageViewer control without touching any of the "view" or "item" property or methods. These shortcuts perform all the necessary check to make sure an active item is added to the viewer. For example, ImageViewer.Image get method is implemented like this:

if (this.ActiveItem != null) // Do we have an active item? 
   return this.ActiveItem.Image; // Yes, return its image 
else 
   return null; // No, return null 

And the set method:

if (this.ActiveItem != null) // Do we have an active item? 
   this.ActiveItem.Image = value; // Yes, set its image 
// Else, nothing to do 

The following lists all the single item mode shortcuts and the equivalent internal code:

In addition to these shortcuts, the following are members used only when ImageViewer is used in single item mode: