It’s not entirely clear what you mean by correlation.If you’re looking to compute the cross-correlation between two images, you can usexcorr2. If you need the normalized cross-correlation, you can usenormxcorr2.
If you want to align two images, you can check out the availableImage Registrationsolutions.
Thexcorr2andnormxcorr2functions mentioned earlier would not perform well with images that have undergone scaling, rotation and other geometric transformations. Some of the feature extractors available in the CVTare robust to that.
If you’re looking for image quality metrics, those are available on this page:Image Quality.
The Image Processing Toolbox and the Computer Vision Toolbox offer many useful tools. Deciding what’s best depends on your use case.