x = fast_gp(b, lambda, pars)
Solves min ||x – b||_F^2 + 2\lambda TV(x)
b is the constant term in the Frobenius norm. lambda is the weight on the total variation penalty. pars is a structure with additional parameters: tol is the cutoff for the normed difference between successive iterates. If the difference falls below tol, the algorithm terminates. max_iters is the maximum number of iterations. bnds is a vector of the lower and upper bounds on the signal. dom is a binary matrix that equals 1 for all pixels in the non-zero support set. tv_type is the type of total variation penalty to use. Must be 'isotropic' or 'anisotropic'.
A. Beck and M. Teboulle, “Fast gradient-based algorithms for constrained total variation deblurring and denoising problems.” IEEE Transactions in Image Processing, vol. 18, no. 11, pp. 2419-2434, Nov. 2009.