iOS指定位置拉扯图片

UIImage * CharacterBtnImage = [UIImage imageNamed:@"whiteBack"];    CharacterBtnImage = [CharacterBtnImage stretchableImageWithLeftCapWidth:CharacterBtnImage.size.width * 0.5 topCapHeight:CharacterBtnImage.size.height * 0.5];    UIButton * btn1 = [UIButton buttonWithType:UIButtonTypeCustom];    btn1.frame = CGRectMake(10, 100, 280, 50);    [btn1 setTitle:@"登陆" forState:UIControlStateNormal];    [btn1 setTitleColor:[UIColor redColor] forState:UIControlStateNormal];    [self.view addSubview:btn1];    // 这里一定要用 setBackgroundImage    [btn1 setBackgroundImage:CharacterBtnImage forState:UIControlStateNormal];