GpsMapEdit can adjust the zoom levels of maps/tiles.
But as already noted I think you have to convert to .mp, edit, then convert back to .img.
I use TypViewer to edit any .typ files, and replace them in the .img using GMapTool.

I'm not sure if there's any software out there that can do everything in the one program, possibly there is, but I don't know of any.


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