This function will soon be added to MapZone, but for now here is a tip to transform a Color Gradient to Grayscale.
This is very usefull when you are building your bump/normal map from the diffuse texture.

Here is a colorized Fractal map, it is the base of a rusty texture. In order to get the main map for the relief we have to transform the color gradient and then adjust the grayscale values.
To do that, follow this procedure until the function will be implemented :