Thanks, but I wrote a much more clever VT chopping utility:
virtualtex that many people have used meanwhile...Also there is the GIMP that is also free for all OS and can do such things much better.
In fact, after more careful examination, your spec-map is really not good, I am afraid. There is a mismatch of 1-3 pixels with the main texture that gives very nasty black seams along lakes and seashore. Also one should always apply some smoothing of the digital zig-zag borders after blowing things up, etc.
I am surprised why you wrote that the original textures were in PNG format, since in the archives they are always in
RAW bin format. This format is almost like PNG, but has NO header. If you read this format as PNG, you will get a misalignment by some pixels that could be the reason for the apparent problems...
I think I will redo the whole stuff, notably including
the very recent matched
3 arc-second SRTM topographic dataset (Shuttle Radar Topography Mission, [JPL, 2005]) using directly Chris 16bit normal-map generator nm16. This will give a most crisp and perfectly matching elevation map exactly at 64k size.
A properly done 64k matched set of base texture, normal-map and spec-texture will give a much more crisp display for sure than your present blown-up "128k".
Anyway, many thanks for your pioneering efforts...
Bye Fridger