[Award Winner] Using the mosaic filter to make towns in Gimp

[torstan]

Now, set the threshold to 0 - this is important as otherwise you'll end up with some slightly transparent buildings. Click the magic wand on the road and you'll get a selection that encompasses the road and all the houses that are adjacent to it.

Now make sure the black and white mosaic layer is selected and go to Edit->Fill with Background colour to fill the selection with white (or ctrl-. for quick).

Do not get rid of the selection, we want to put some of those buildings back in again.

You should now have something like this:



To replace some of those houses we need a little bit of trickery. Take the following steps:
1. Make sure the Roads layer is selected.
2. Go back to the magic wand and deselect the Sample Merged option.
3. Change the selection preferences to Subtract from Selection.

Your tools window should now look like this:



Now click on the black road. Now you just have the white space selected where you want to replace buildings. However this still borders the road, so if we just fill that with black then we'll be back where we started. To get around this do the following.
1. Go to Select->Shrink... and shrink your selection by 2 pixels, leave all other options at their default.
2. Go to Select->Grow... and grow by one pixel.

This has the effect of getting rid of tiny areas and retaining larger ones.

3. Make sure your black and white mosaic layer is selected.
4. Go to Edit->Fill with Foreground colour (or ctrl-, for quick).

You should now have something that looks like this:



Essentially we are now done, having created a mask that has all of our houses in it. Now the challenge is to make this pretty. I'll address this in the next post.