The technique I use is to superimpose the map_c over the map_h and to follow the valleys on the map_h to locate the course of the river you wish to draw in.
You have to actually draw in the river with a graphic drawing tool. The river should be at least 3 pixels wide and you should blur it with "gaussian blur" after drawing in each chunk. This will give it some texture. Values up to RGB127 will translate as water and over that will be rendered as land. The higher the value up to 127, the shallower your water will be.
Try and avoid perfectly straight lines and rigid angles as these look unnatural on the finished product.
It takes a lot of work and a lot of trial and error.
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I think that it is much less tedious to copy rivers (after selecting blue colour as a layer) from Free Relief Layers for Google Maps
http://www.maps-for-free.com/
I have just Browsed map-for-free site,but cant not download anything.how to use it?
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Fenbeiduo Wrote:I have just Browsed map-for-free site,but cant not download anything.how to use it?
I am using ScreenGrab pgm, it is free , Google it.
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Fenbeiduo Wrote:Thanks Uzin,U mean we cant download maps except grab it ?
Read Tutorial: you can also use Snapshot there included, whatever is more convenient to you.