A new family of Polak–Ribière–Polyak conjugate gradient method for impulse noise removal

This paper discusses a new class of the Polak–Ribière–Polyak (PRP) conjugate gradient methods for an impulse noise removal problem, which is transformed into an unconstrained optimization problem with smooth objective function. Our new class contains the four improved conjugate gradient directions, three of which are regularized versions of PRP conjugate gradient directions and last of which is is the combination of Fletcher–Reeves and PRP conjugate gradient directions. It is shown on several known images that our new methods are more robust and efficient than other known methods for impulse noise removal.