ios 截屏

 + (instancetype)captureWithView:(UIView *)view
{
    // 1.开启上下文
    UIGraphicsBeginImageContextWithOptions(view.frame.size, NO, 0.0);
    
    // 2.将控制器view的layer渲染到上下文
    [view.layer renderInContext:UIGraphicsGetCurrentContext()];
    
    // 3.取出图片
    UIImage *newImage = UIGraphicsGetImageFromCurrentImageContext();
    
    // 4.结束上下文
    UIGraphicsEndImageContext();
    
    return newImage;
}