$E_{f_2}$	${\ell }_2$-norm fidelity term
$E_{f_1}$	${\ell }_1$-norm fidelity term
$E_{tv}$	TV (total variation) regularization term
$E_{aho}$	Anisotropic high order regularization term
$\mathrm{a}(·)$	The area of $(·)$
$\mathrm{len}(·)$	The length of $(·)$
∇	Gradient operator
$\mathbf{D}$	Anisotropic second order operator