Clustering algorithms by minimizing an object function share a clear drawback that the number of clusters need to be set manually. Although density peak clustering is able to seek the number of clusters, it suffers from memory overflow when it is used for image segmentation because a moderate-size image usually includes a large number of pixels leading to a huge similarity matrix. To address the issue, here we proposed an automatic fuzzy clustering framework (AFCF) for image segmentation. The proposed framework has threefold contributions. Firstly, the idea of superpixel is used for the density peak (DP) algorithm, which efficiently reduces the size of the similarity matrix and thus improves the computational efficiency of the DP algorithm. Secondly, we employ a density balance algorithm to obtain a more robust decision-graph that helps the DP algorithm to achieve fully automatic clustering. Finally, a fuzzy c-means clustering based on prior entropy is used in the framework to improve image segmentation results. Because the spatial neighboring information of both the pixels and membership are considered, the final segmentation result is improved effectively. Experiments show that the proposed framework is not only able to achieve automatic image segmentation, it also provides better segmentation results than state-of-the-art algorithms.Index Terms-Fuzzy clustering, image segmentation, superpixel, density peak (DP) algorithm Tao Lei (M'17) received the Ph.D degree in Information and Communication Engineering from Northwestern