UIImage点九图（让image不变形、只拉伸中间部分）

建议写成UIImage的分类，如下

.h

//保证图片拉伸不变形
- (UIImage *)resizingImageState;

.m

//保证图片拉伸不变形
- (UIImage *)resizingImageState
{
    CGFloat imageW = self.size.width * 0.5;
    CGFloat imageH = self.size.height * 0.5;
    UIImage *newImage = [self resizableImageWithCapInsets:UIEdgeInsetsMake(imageH, imageW, imageH, imageW) resizingMode:UIImageResizingModeStretch];
    return newImage;
}