imageView背景图片拉抻

代码示例：

     UIImage *image=[UIImage imageNamed:@"**1"];

    UIImage *imageSel=[UIImage   imageNamed:@"**1Sel"];

    image=[image stretchableImageWithLeftCapWidth:image.size.width*0.5topCapHeight:image.size.height*0.5];或者

[image resizableImageWithCapInsets:UIEdgeInsetsMake(image.size.height*0.5, image.size.width*0.5,image.size.height*0.5, image.size.width)*0.5];

    imageSel=[imageSel stretchableImageWithLeftCapWidth:imageSel.size.width*0.5topCapHeight:imageSel.size.height*0.5];