Image/Drawing pixel comparison tool

I'm currently doing software testing of a CAD software and there are many scenerio where i need to compare the drawings.

Like for example there is a tool "X", If i use that tool it will create a circle based on the parameters,What i want to test is if we gave the same parameters again and use that tool whether i'm getting the same circle as before or Is there any changes ?

So i would like to ask the stack-overflow community for suggestions regarding the software tools which is apt for testing these kind of test cases and the methodology of testing.