Dear  Dr Shahid

 To detect objects you can use various object detection algorithms. After that, you can just get the object from most upper coordinates from your image. Will you please give some images as examples, then I can give you specific solution regarding that. You can visit the link that I have provided. It will help you.

Regards

Ehtesham Chowdhury

http://docs.opencv.org/2.4/doc/tutorials/objdetect/table_of_content_objdetect/table_of_content_objdetect.html

What kind of objects are you trying to detect?

Take a look to dlib library