Round Rect Button behavior when using a flipview controller

Hia.

I am using some round rect buttons with own images for their states. Each time am displaying a different view for some stuff,开发者_开发问答 the buttons become white and my images are fading in briefly later.

The problem occurs only with the UIModalTransitionStyleCrossDissolve animation. The other 3, UIModalTransitionStyleCoverVertical, UIModalTransitionStyleFlipHorizontal and UIModalTransitionStylePartialCurl, don't show this effect.

The effect would be ok, ok if the starting color would be black. I didn't find any way to change that color in IB. Where does it come from? Any idea?

Tried to set the background over the inherited properties of UIImage, but he simply ignored it. Switching the Round rect button to a custom one solved it. Leaves the question what to do if I want a round rect. A black background image didn't help. He seems to use the background color to fade.