How to take a screenshot programmatically on iOS

I want a screenshot of the image on the screen saved into the saved photo library.

Solution

I'm answering this question as it's a highly viewed, and there are many answers out there plus there's Swift and Obj-C.

Disclaimer This is not my code, nor my answers, this is only to help people that land here find a quick answer. There are links to the original answers to give credit where credit is due!! Please honor the original answers with a +1 if you use their answer!

Using QuartzCore

#import <QuartzCore/QuartzCore.h> 

if ([[UIScreen mainScreen] respondsToSelector:@selector(scale)]) {
    UIGraphicsBeginImageContextWithOptions(self.window.bounds.size, NO, [UIScreen mainScreen].scale);
} else {
    UIGraphicsBeginImageContext(self.window.bounds.size);
}

[self.window.layer renderInContext:UIGraphicsGetCurrentContext()];
UIImage *image = UIGraphicsGetImageFromCurrentImageContext();
UIGraphicsEndImageContext();
NSData *imageData = UIImagePNGRepresentation(image);
if (imageData) {
    [imageData writeToFile:@"screenshot.png" atomically:YES];
} else {
    NSLog(@"error while taking screenshot");
}

In Swift

func captureScreen() -> UIImage
{

    UIGraphicsBeginImageContextWithOptions(self.view.bounds.size, false, 0);

    self.view.drawViewHierarchyInRect(view.bounds, afterScreenUpdates: true)

    let image: UIImage = UIGraphicsGetImageFromCurrentImageContext()

    UIGraphicsEndImageContext()

    return image
}

Note: As the nature with programming, updates may need to be done so please edit or let me know! *Also if I failed to include an answer/method worth including feel free to let me know as well!