PNG Fourth Edition, which we are working on now, is likely to add gain maps. However, gain maps are extra data. So there is a trade off. The reason gain maps

PNG Fourth Edition, which we are working on now, is likely to add gain maps. However, gain maps are extra data. So there is a trade off. The reason gain maps didn't make it into Third Edition is it isn't yet a formal standard. We have a bunch of the work ready to go once their standard launches.