Calabash backdoor method to capture screenshot and save it to Photos

appDelegate.m

- (NSString *)takeScreenShot:(NSString *)aIgnore
{
    UIViewController* viewController = (UIViewController*) self.window.rootViewController;
    
    UIGraphicsBeginImageContextWithOptions(viewController.view.bounds.size, viewController.view.opaque, 0.0);
    [viewController.view.layer renderInContext:UIGraphicsGetCurrentContext()];
    UIImage *image = UIGraphicsGetImageFromCurrentImageContext();
    UIGraphicsEndImageContext();
    
    NSData *imageData = UIImagePNGRepresentation(image);
    [imageData writeToFile:@"shot.PNG" atomically:YES];
    
    UIImageWriteToSavedPhotosAlbum(image, nil, NULL, NULL);
    
    return @"true";
}

calabash-ios console output

irb(main):005:0> backdoor('takeScreenShot', '')
"true"

screencast

http://www.screencast.com/t/jsm9x8Z9