ios - Take screen in particular view in iphone with camera preview

Question

CGRect screenRect = [[UIScreen mainScreen] bounds];
    UIGraphicsBeginImageContext(screenRect.size);
    CGContextRef ctx = UIGraphicsGetCurrentContext();
    [[UIColor whiteColor] set];
    CGContextFillRect(ctx, screenRect);
    [self.view.layer renderInContext:ctx];
    UIImage *img = UIGraphicsGetImageFromCurrentImageContext();
    UIGraphicsEndImageContext();

    return img;

Now I m using this to take screen shot. It works well but the camera preview shows black. I need to take screen shot with camera preview for both IOS6 and IOS7. Any suggestion greatly appreceatable..