Image restoration with precondition conjugate gradient method

Image restoration can be attributed to solving a linear systems and conjugate gradient method is an effective iteration algorithm for solving various linear systems. However the convergence rate of CGM is determined by condition number of coefficient matrix. The level1 and level2 preconditioner were used to reduce the condition number of coefficient matrix and to accelerate the convergence rate. Simulation experiment show that with same iteration times the PCGM reached better results than other methods.