I was grokking and ended with some masks that can be used in iMaginator or Create. They are Grayscale JPGs.
In iMaginator: Open them. Color Invert. Mask To Alpha. I include a Color Invert & Mask Effect Chain. You can do other Effects also - Colorize, Blur...)
I then drag a png (or tiff) from the Image Drag Well in iMaginator to Create in order to place over a Graphic or Image.
The Effected files can also used for Source Out in iMaginator
I store the jpg files in an iMaginator Gallery.The tar-ball is all the files together, if you want to expand it and import the folder as a Gallery. Ones that I've Effected I store in a Create Library Resource.
Hope you can use them,
It's very cool that you can drag straight from the iMaginator Galleries straight to Create.