顶部header图片拉伸放大

实现UIScrollViewDelegate的代理方法

- (void)scrollViewDidScroll:(UIScrollView *)scrollView

{

CGFloat offsetY = scrollView.contentOffset.y;

if (offsetY<0) {

CGFloat scale = 1- (offsetY/50);

scale = (scale>=1)?scale:1;

self.topImage.transform = CGAffineTransformMakeScale(scale, scale);

}

}