Custom mask
Make certain parts of your application's window transparent. You can use this option to make a custom window shape for your application.
To specify the areas that you want to make transparent, you need to create a transparency mask file in your favorite drawing program.
A transparency mask file is just an image where a single color represents the parts that you want to make transparent. Picture this image as being invisibly "placed over" your application's window, like a mask or a stencil.
In AutoPlay, the transparent parts of the mask should all be solid black. Wherever solid black appears in the mask image, the corresponding part of the window will be made transparent. The transparency mask acts like a "cookie cutter," cutting holes in the application's window so the user's desktop can show through.
Click the browse button to select an image file.