We need a bumpmap texture, in grayscale if wanted, but actually, not needed.
Then, we emboss in the red and green channels, as follow. To emboss a channel, you click on them in the channels menu. The red channel must be embossed so the lighting is on the right
This is done with: Filter/Stylize/emboss (or how ever is written in english, i know the spanish of it, "relieve") The values used here are 3 pixels long, 100% depth, in both cases.
And the green channel has the lighting on top.
Finally, the blue channel. The blue channel is tricky, If we understand the normal maps, the blue means the normal we want facin us. The way we get this effect is to search for the borders in the image.
This is done with: Filter/Stylize/Find Edges
But this effect is too hard, we would get a normal map too defined in the "Z" axis (properly the "normal"), so we need to clarify this blue channel, what is up to the user, but a value of whitening that made the darkest color 25% grey, would be good (IMO, this is purelly experimental)
And this is the result!
Now, if you need a normals map, you only need one bump map, and some filters.I hope you find this useful!
Although this is photoshop done, i guess that other programs that can work with the image channels can do the same. Try yourselves.
This image shows the normal map at work.
