/**
*截取scrollview整个图片
*/
UIGraphicsBeginImageContext(_scrollView.contentSize);
{
CGPoint savedContentOffset = _scrollView.contentOffset;
CGRect savedFrame = _scrollView.frame;
_scrollView.contentOffset = CGPointZero;
_scrollView.frame = CGRectMake(0,0, _scrollView.contentSize.width, _scrollView.contentSize.height);
[_scrollView.layer renderInContext: UIGraphicsGetCurrentContext()];
_viewImage = UIGraphicsGetImageFromCurrentImageContext();
_scrollView.contentOffset = savedContentOffset;
_scrollView.frame = savedFrame;
}
UIGraphicsEndImageContext();
