Fig. 1. Flow chart of image super-resolution reconstruction based on hierarchical clustering

Fig. 2. Flow chart of multi-dictionary learning

Fig. 3. Flow chart of hierarchical clustering of agglomerative nesting and divisive analysis

Fig. 4. Structure diagram of hierarchical clustering of 20 samples

Fig. 5. Structure diagram of hierarchical clustering of 5000 samples

Fig. 6. Standard test images. (a) Parrots; (b) Bike; (c) Hat; (d) Lena; (e) Peppers; (f) Leaves

Fig. 7. Reconstruction images of Leaves using different algorithms. (a) Original image; (b) bicubic interpolation algorithm; (c) algorithm proposed by Yang et al.[8]; (d) algorithm proposed by Dong et al.[9]; (e) algorithm proposed by Peleg et al.[10]; (f) our algorithm

Fig. 8. Reconstruction images of Lena using different algorithms. (a) Original image; (b) bicubic interpolation algorithm; (c) algorithm proposed by Yang et al.[8]; (d) algorithm proposed by Dong et al.[9]; (e) algorithm proposed by Peleg et al.[10]; (f) our algorithm

Fig. 9. Local reconstruction images of Leaves and Lena using different algorithms. (a) Bicubic interpolation algorithm; (b) algorithm proposed by Yang et al.[8]; (c) algorithm proposed by Dong et al.[9]; (d) algorithm proposed by Peleg et al.[10]; (e) our algorithm

Fig. 10. (a) PSNR and (b) SSIM line diagrams of reconstruction images with different algorithms