Image comparison software to detect missing objects

We are looking for an image comparison software that will compare 2 images taken by a camera for some tools and see if the tool is missing a part or not (usually tool could miss a nut or screw or bolt..) We need a quick program for demo purposes to our client as we are trying to make a proof of concept. successful candidate who will win the project for this demo software (has to be completed in 5 days max) will win the big project which is based on same concept but will require much more functionalities in the software and more customization. As explained this is just demo to make a proof of concept for the customer that we can successfully detect the missing parts. the software should have: 1- simple interface for adding the original picture and then the 2nd picture after part is missing (they should be beside each other and then the bottom half of the screen showing the result picture with the missing part marked (i will upload screen shot) 2- image comparison shouldn't take long should be few seconds only 3- the expected final project will be around 4,000-5000 US$ but this demo is limited to 350$ as we are just using it to demo but not real use. who wins the demo project and proof his capability of handling it will win the big project automatically 4- this is not pixel to pixel comparison it is image to image because images taken by camera will be shifted a little bit , i can't take exact same picture 5- project must be completed in 5 days for the demo version after that life project we can do 2 months when we work with a developer and we found him good we establish a long term relation for many other projects