Table 2.

Experimental testing: comparing the average computing time of DCBFC to the other methods under different image size.

Image Size	DCBFC	K-means	Hierarchical	Spectral	PCA-k-means	PCA-hierarchical	Spectral-threshold
$128\times 128$	$5.6\pm 0.4\mathrm{s}$	$286.7\pm 247.0\mathrm{s}$	$4677.1\pm 1565.9\mathrm{s}$	$9.2\pm 1.1\mathrm{s}$	$89.3\pm 92.6\mathrm{s}$	$1614.9\pm 66.0\mathrm{s}$	$8.6\pm 0.8\mathrm{s}$
$256\times 256$	$79.8\pm 1.6\mathrm{s}$	$1038.0\pm 166.7\mathrm{s}$	$31.2\pm 0.5\mathrm{h}$	$88.3\pm 2.0\mathrm{s}$	$166.4\pm 90.9\mathrm{s}$	$29.0\pm 1.2\mathrm{h}$	$131.0\pm 4.8\mathrm{s}$

Note: Hierarchical and PCA-hierarchical were calculated in hours (h) at $256\times 256$ image size. Others were measured in seconds (s).