iOS 解决按钮背景图片拉伸问题(推荐)

- (void)awakeFromNib
{
  [super awakeFromNib];
  //让背景图片不要拉伸
  UIImage *image = _loginRegisterBtn.currentBackgroundImage;
  image = [image stretchableImageWithLeftCapWidth:image.size.width / 2 topCapHeight:image.size.height / 2];
  [_loginRegisterBtn setBackgroundImage:image forState:UIControlStateNormal];
}