[lowfighter]

Been doing too millions of experiments. So far this one looks promissing: start with a 1 pixel river (rgb=0). Apply simple (not Gaussian) blur. Look in game: it is very narrow (maybe 20-50 m) but it has a lot of discontinuities. Go back to gimp and select the blured thing and make a lot of copies. To each copy apply brightnes reduction ( I decreased in steps of 10). Back to game. As the copies got darker the discontinuities began to disappear but when all gone the river was to wide say about 100 m. However looking at the copy with 20 reduction in brightnes, that looked the best, not many discontinuities and also pretty narrow. Back to gimp and look at the discontinuities. Picked the lowest gray and painted them. Still we need a faster method since we don't want to spend ages at each Km of river...Here's some pics of the same river, average width I think maybe 50m, sometimes width reach close to 100 sometimes... Still digging