How to find best match for single image from multiple images?

Given: I have one reference image (RefIm), and stack of other similar images (StackIms), with slight different intensity.

Want: I want to find the best match image for RefIm from StackIms.

Currently Done: Currently I'm using using the 'imregtform' followed by 'imfuse' to register and match image, but I can do it only for single image. I could add for loop, but what parameter I should use to compare?

Needed: I'm wondering what would be the parameter or value I should use to find best match for the reference image from multiple image stack.

If you any other suggestions/ideas/algorithms or questions, please let me know.

[ACKNOWLEDGMENTS]

I will vote for all your answers.

Thank you for any help.

Answer 1

[Joseph Cheng]

I'm not sure what the imfuse gets you besides something to see but why not calculate the structural similarity of the images to the reference? quick search brought the wiki page https://en.wikipedia.org/wiki/Structural_similarity

and matlab has a built in function http://www.mathworks.com/help/images/ref/ssim.html