Tests done.
Yes, it seems the slow-down was entirely due to the small pixel dimensions of the image and seemingly not the mask effect. To test this I used an image a 1/4 size of the screen with TileImage and my mouse pointer danced around as smooth as silk. :)
Yes, it seems the slow-down was entirely due to the small pixel dimensions of the image and seemingly not the mask effect. To test this I used an image a 1/4 size of the screen with TileImage and my mouse pointer danced around as smooth as silk. :)