A better way to remove lighting information from source is to either magic wand the shadows or select color range til your shadowed areas are all selected. Then select>modify>expand by a few pixels. Then select>modify>feather half of what you expanded by.
Then run filters>other>offset to fill the selections
For example Mayang texture:
http://www.mayang.com/textures/Stone/images/Rock%20and%20Objects/stone_5160235.JPG
Becomes :