252028aaac
Add predictive filtering option for Alpha plane. Valid range for filter option is [0, 5] corresponding to prediction methods none, horizontal, vertical, gradient & paeth filter. The prediction method 5 will try all the prediction methods (0 to 4) and pick the prediction method that gives best compression. Change-Id: I9244d4a9c5017501a9696c7cec5045f04c16d49b