Pixel Data Access is an interprocess communication technique that enables users of graphical user interfaces to automate certain tasks. By accessing the contents of the display buffer, users can search for pixel representations of interface elements, and then initiate actions such as mouse clicks and keyboard entries. While this technique has limitations it offers users of current systems some unusually powerful features that are especially appealing in the area of end-user programming. Also cross-referenced as UMIACS-TR-99-27