image not showing in UIBUtton

I'm writing a small application that allows for patterns to be placed on a button. When I run the app in the simulator the patterns display ok on the button. When I compile the application to the device the patterns do not display on the buttons but all other logic behind the buttons works fine.

The patterns are simple png images and I use the basic code:

[orangeButton setImage:[UIImage imageNamed:@"circle.png"] forState:UIControlStateNormal]开发者_Go百科;

to add the patterns to the buttons.

To bring the patterns into Xcode I have just dragged them from the desktop to the resources folder in Xcode.

Why are the patterns displayed in the similuator but not the provisioned application?

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The device is case-sensitive, the Mac is not; this may be the problem.