I have a very confused question. When calculating the similarity of two identical images, the value obtained should be 1 or greater than 1 (because I don’t know whether the value is normalized or not), but a very strange problem arises. The value obtained is more than - 0.8. There are two problems: (1) the problem of negative value. I have consulted the documents and papers, and understand that it is caused by the definition. (2) If the value is more than 0.8, I don’t know how to understand it. The metric I use is “jointhistogrammutualinformation”.
And when I rotate the registered floating image 1 ° in one direction (or 1 mm translation), I find that the calculated value is better than the registered value. Is this the problem of registration algorithm?