图片拉伸方法以及修改图片渲染模式以及如何把一个控制器包装成一个导航控制器

- (void)viewDidLoad {
    [super viewDidLoad];

    UIImage *NormalImg = [UIImage imageNamed:@"RedButton"];
    UIImage *HightImg = [UIImage imageNamed:@"RedButtonPressed"];
    
    
    //对图片做拉伸
    NormalImg = [NormalImg stretchableImageWithLeftCapWidth:NormalImg.size.width *0.5 topCapHeight:NormalImg.size.height *0.5];
    HightImg = [HightImg stretchableImageWithLeftCapWidth:HightImg.size.width *0.5 topCapHeight:HightImg.size.height *0.5];
    self.NormalImg = NormalImg;
    self.HightImg = HightImg;
    
    //给按钮设置背景图片
    [self setBackImgWithBtn:self.LoginBtn];
    [self setBackImgWithBtn:self.zhuCeBtn];
    
  
}
//给图片设置两种状态下的背景图片方法
- (void)setBackImgWithBtn:(UIButton *)btn{
    [btn setBackgroundImage:self.NormalImg forState:UIControlStateNormal];
    [btn setBackgroundImage:self.HightImg forState:UIControlStateHighlighted];
    
}