(a) The original lunar gray image (resolution: 128 × 128) with S = 1,739 nonzero values. The random Gaussian measurement number of CS over this image is M = 3S = 5,217 measurements, which is . (b) The reconstructed image using conventional CoSaMP recovery method. (c)-(f) The images reconstructed with 2, 5, 10 and 50 clusters of values for intensities CoSaMPs. The computational time is (b) 5.82 s (c) 2.94 s (d) 3.24 s (e) 5.74 s and (f) 10.36 s.