In this paper, a structural similarity index is first proposed for two images with possibly different dynamic ranges and intensities as well as possibly small rotation and translation. The proposed index is then extended by dividing two images into local windows, and the similarity is detected by checking all pairs of local windows. It is shown by experimental results that the proposed indices are more robust to large intensity and dynamic range changes of two images from the same scene than the structural similarity (SSIM) index in [4].