Mercator-style coloring in GIMP

[Rubberduck]

I was asked how I made the coloring on my map in this other thread ( http://www.cartographersguild.com/showthread.php?t=6054 ). So I've thrown together this short tutorial.

Of course, I developed this technique, while trying to emulate Ascension's Antique-style maps in Photoshop, so props definitely goes to him.

Now for the tutorial:

1: First you gotta have a landmass. I this case, I made a fractal shape using CC3.
tut1.JPG

2: Then we paint it black, or any other color, as long as it is a single color with a sharp edge. We'll keep this one around as our definition between what is land and what is sea. Name the layer "Land/Sea Solid".
tut2.JPG

3: Next we create a new layer. This is where we will define our country borders. Call it "Countries Solid" and make sure its above the Land/Sea Solid layer. Then we paint our country borders in different colors in this layer. Use the pencil, we don't want blur at the edges. And no need to worry about coastlines. Just make sure that you don't use the same color at two neighboring countries.
tut3.JPG

4. Now go back to the"Land/Sea Solid layer, and select the sea with the Fuzzy Select Tool. Choose the Countries Solid layer without removing the selection. And press delete. Voila, your borders now fits the coastlines.
tut4.JPG

[Rubberduck]

5. Now create a new layer above the two previous, and call it "Background". Here you enter the background color or picture that you want. In this case I used a pergamenty type color.
tut5.JPG

6. Create two more layers above the background. The bottom one is "Countries Interior", the top one is "Countries Border". Set the Countries Interior layer to 10% opacity.

7. Now comes the fun part. Make the Background layer invisible, and go to the Countries Solid layer. Use the Fuzzy Select Tool to select the nations that you want to be the same color. Use "add to the current selection" to make sure that you have them all selected at the same time. You can do each country seperately, but it's easier to do them all together.

8. Go up to the Countries Interior layer. Using the Bucket Fill Tool, paint the countries in the color that you want the border to be. If you under "Affected Area" choose "Fill While Selection", you'll fill all the countries at the same time with one click. In this case I chose a dark green, which you might not be able to see, but trust me, it there is a difference when you turn the Background on.
tut6.JPG

9. Next choose the Airbrush Tool. Set brush to "Circle, Fuzzy 19". Depending on the size of your map, you may want a scale setting larger or smaller than the default 1. You might be surprised how large a brush you'll need, but if it is too small, you can always undo and take a bigger brush. For this 2000 x 2000 pixels picture scale 5 fit the bill.

10. Now change to the Countries Border layer, and chose Edit -> Stroke Selection -> Stroke with a paint tool -> Airbrush and click stroke.
tut8.JPG

11. Finally invert your selection and press delete to remove the paint that was outside of the borders. Your first batch of countries are all done.
tut9.JPG

[Rubberduck]

12. Repeat the process for the other countries with one exception. At step 10 and 11, create a temporary layer above the Countries Border layer for the stroking and spill deletion, and then merge down the temporary layer into the Countries Border layer once you are done.
tut10.JPG
tut11.JPG

13. Doing the sea isn't any harder. Just go to the Land/Sea Solid layer and select the Sea with the fuzzy tool, the use the same method as you've used for the countries.
tut12.JPG

And that's it. Easy peasy.

[Alecthar]

You can find out the ID numbers for your attachments and then distribute them more naturally in your instructions using the [ATTACH] tag. Just click through to the full version of your attached picture, then copy the 5 digit number after "attachmentid=" and put it in between your [ATTACH] and your [/ATTACH].