I've recently added in a radial gradient overlay to show the user where the blur is on the screen.
It's done using CoreGraphics and the code can be seen in the drawRect method of BlurOverlayView.m.
I've noticed it's a bit laggy on iPhone 4 and 4S, so if anyone with some CoreGraphics foo would mind helping out, I'd appreciate it.
I solved this by making the BlurOverlayView double the size of the frame, put it in a UIScrollView, and manipulated the scroll view on panning and zooming instead of re-rendering the radial overlay instead. Only when I detect that the pan/pinch has ended from the gesture recognizers then do I call [staticPicture processImage].
Let me know if you would like a proper pull request.
Yeah I'll take a look at your branch, thanks!
@leejunkit so I took a look at it, and it's definitely faster, but it doesn't feel or look as nice as the current version. Thanks the great idea though. I may borrow from some of your code when I revisit this.