（IOS）image拉伸

+ (UIImage *)resizableImage:(NSString *)imageName

{

    UIImage *image = [UIImage imageNamed:imageName];

    CGFloat imageW = image.size.width;

    CGFloat imageH = image.size.height;

    return[image resizableImageWithCapInsets:UIEdgeInsetsMake(imageH *0.5, imageW *0.5, imageH *0.5, imageW *0.5) resizingMode:UIImageResizingModeStretch];

}