Is there a way of adjusting the screen brightness programmatically?

I have an iPhone app for 开发者_运维百科photographic purposes (kind of a lightbox). This app needs as much brightness as possible. Is there a way to change the screen brightness programmatically, and then restore it back some time later?

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Edit: iOS 5 now includes a screen brightness API.

[[UIScreen mainScreen] setBrightness:0.5];

Previous answer:

No, this capability is not exposed via public APIS.

Edit: Note that a future possible iOS release may or may not have screen brightness on the multitasking bar on one particular iDevice.

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It is possible, but your app will most likely get rejected from the App Store, because it uses a private API. A flashlight-app was rejected because it adjusted the screen brightness, so I wouldn't recommend it.

In iOS 4.2, the iPad will have a screen brightness-adjuster in the multitasking-bar,

(as mentioned by @coob) so you could tell your users to set the brightness there.

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What you could do, is to create a black overlay-view, and set it's alpha to more or less, according to how bright you want the screen to be. This won't actually make the screen less/more bright, but it will give the user an illusion of that.

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Here's a Swift answer to this question.

import UIKit
extension UIScreen
{
    static func setMainBrightness(brightness: CGFloat)
    {
        guard (0...1).contains(brightness) else
        {
            print("Attempt to set the screen brightness to an invalid value: \(brightness) should be between 0 and 1 inclusive.")
            return
        }
        self.main.brightness = brightness
    }
}

Call it by using:

UIScreen.setMainBrightness(0.5)

Or ignore my extension (which I just wrote to illustrate the limits) and just call:

UIScreen.main.brightness = 0.5