Is there a way to import the wilbur file into gimp?

For example, i want to use wilbur to dig my lakes so i can better control my depth rather then using gimp to try and make it look right. Would there be a way to get what i see on wilbur into gimp so i can place it on my world map? I tried to save it as a png and load that but it just loaded up a black and white flat image. (I assume that's what wilbur uses to show its height and depth.)

I know i could just take a screen capture of the lake in wilbur and then copy that over but then it wouldn't be very high quality. If there is no other way, i may use that though.