UIImage *image;
CGFloat top = 10; // 顶端点(若拉伸 这个点会一直重复复制)
CGFloat bottom = 10 ; // 底端点
CGFloat left = 10; // 左端点
CGFloat right = 10; // 右端点
UIEdgeInsets insets = UIEdgeInsetsMake(top, left, bottom, right);
image = [image resizableImageWithCapInsets:insets resizingMode:UIImageResizingModeStretch];