Similarity assessment of quantum images

Similarity assessment of quantum images is important in the area of quantum image processing. In this paper, quantum counting is applied to five algorithms for similarity assessment of quantum images, which brings an advantage to the number of quantum measurement. Among these algorithms, one algorithm is suitable for quantum binary image, two algorithms are suitable for quantum gray image and two algorithms are suitable for quantum color images. Moreover, the similarity assessment of quantum gray and color images involves two quantum image binarization algorithms. At the end of the paper, the quantum circuit complexity of these algorithms is analyzed and then an example is given to demonstrate the functionality of the algorithm.