"DesktopImage" is a Cocoa sample application that demonstrates how to use the NSDesktopImages category of NSWorkspace.  It shows how to use this set of APIs to set the desktop image for a given screen.  An NSURL is used to describe that image.
An "options" dictionary controls how the image is presented: scaling factor, clipping state which affects the interpretation of Proportional scaling types, and fill color applied to any empty space around the image.
Sample Requirements
The supplied Xcode project was created using Xcode v4.4 running under Mac OS X 10.8 or later.
This sample is also App Sandboxed.
Using the Sample
Build and run the sample using Xcode.  At the top of the window select which monitor you want to be affected.  Then apply any of the 3 screen options.  Next choose the image from a grid of images.  You can browse to another directory by using the path popup control at the bottom.
To review the code that sets the desktop image, refer to this method in ControllerBrowsing.h:
    - (void)imageBrowserSelectionDidChange:(IKImageBrowserView *)aBrowser
Changes from Previous Versions
1.1 - Upgraded to Xcode 4.4 and Mac OS X 10.8, fixed some compiler warnings, now using NSURL instead of string paths.
1.0 - First version
Packaging List
The main controller class in charge of the app's main window.
An extension or category of Controller class responsible for controlling the IKImageBrowserView.
Copyright (C) 2008-2012 Apple Inc. All rights reserved.