您设置图像视图的内容模式为中心。

尝试设置为看点填充，或根据需要达到什么样的缩放以填充。

I have my UIImageView in the view which will download image from server and after downloading finish then my UIImageView height will be adjusted according to height of image but the problem is it is working perfectly in iOS8 but not in iOS7. In iOS7, the height is scaled to much more than I tried to set. I am setting autolayout via IB

Here is the excerpt from my code (default is 250)

 if(image.size.height<250) headerView.itemImageView.contentMode =      UIViewContentModeCenter;
                 else{


                   adjustedHeight =      image.size.height*320.0f/image.size.width;


                     imageHeight = adjustedHeight;

                     [headerView.heightContraintLayout setConstant:adjustedHeight];
                [headerView.itemImageView layoutIfNeeded];
 //after this line of code, I check the size of itemImageView is extended more than the adjestedHeight that I set in the previous line ( this only happened in iOS7 not iOS8

You set the image view's content mode to "centre".

Try setting it to "Aspect Fill" or "Scale to Fill" according to what you need to achieve.