UIView转为图片

    //UIGraphicsBeginImageContext(CGSizeMake(view.bounds.size.width, view.bounds.size.height)); //刚方法无scale，所以会模糊
    //UIGraphicsBeginImageContextWithOptions(区域大小, 是否是非透明的, 屏幕密度);
    UIGraphicsBeginImageContextWithOptions(view.frame.size, YES, UIScreen.mainScreen.scale);
    [self.portraitBar.layer renderInContext:UIGraphicsGetCurrentContext()];
    UIImage *image = UIGraphicsGetImageFromCurrentImageContext();
    UIGraphicsEndImageContext();