What is Thumbnails view in Windows Explorer, and what is a thumbnail handler?
Windows Explorer can display the contents of folders using several different views. These may vary depending on what version of Windows you are running and what types of files are contained in the folder; typical views include Icons, List, Details, and Thumbnails. In Thumbnails view, Explorer attempts to display a thumbnail of the image instead of its normal icon. Windows has built-in support for several image types, such as bitmap, JPEG, and GIF. It also has a way for developers to write “thumbnail handlers” in order to view thumbnails of other file types. That is exactly what PSP Thumbnail Handler is: it provides Windows Explorer with a thumbnail image to display for files that are in the PSP format.
