Improve the scroll insets of image edition while zooming in and out

[dzenbot]

[cooler333]

same!! Please Fix it

[roadProgram]

对于长图的处理是： CGFloat vInset = fabs((maskHeight-imageSize.height)/2); 更换为 1、CGFloat vInset = fabs(fabs(maskHeight - self.view.frame.size.height)/2 -fabs(imageSize.height - self.imageView.frame.size.height) /2 ); 2、scrollViewDidEndZooming 中增加 _lastZoomScale = self.scrollView.zoomScale; [self updateScrollViewContentInset];