A new key has been added that was missing: GRID2DPATH that can be in intput and output. This key is now properly handled by the appropriate plugins. A new color reduction strategy has been implemented in the gradients and the PNG plugin: instead of reducing the colors coming out of the gradient, the values coming in are discretized. This leads to much more effective size reduction for the same output quality, with 5% speed increase compared to the original code not doing this reduction (test: reading and writing back a grid). The file size is now 1/3 of the full color file.