Mapping Hacks

154

|

Chapter 3, Mapping Your World

#32 Hack on Base Maps in Your Favorite Image Editor

HACK

Importing the Map Layers

Now, let’s switch to our image editor. We like the GIMP, but any advanced

image editor—like Photoshop, for example—will have all of the features

and tools we describe. First, grab the image you want to overlay the politi-

cal boundaries on. We chose the 2048x1024 pixel Blue Marble image from

http://flatplanet.sourceforge.net/maps/natural.html, but any of the images on

that page will do. You can also find a copy of this image at http//

mappinghacks.com/maps/land_shallow_topo_2048.jpg. Save it to your hard

drive, and load it up in your image editor. This image will serve as the base

layer, over which we’ll drape the boundaries layer. Figure 3-37 shows what

this image looks like.

Next, we’ll import the boundaries layer, which we saved earlier as world.ps.

Loading a PostScript file will trigger a dialog that provides the image editor

with some hints about how to rasterize the vector data. In the GIMP, Post-

Script files always load in portrait orientation at 8.5"x11", so the resolution

we select influences how many pixels wide and high the imported image will

be. We want to select a resolution that will make the two images come out

the same size. Since our underlying JPEG image is 2048 pixels wide, we need

to divide 2048 pixels by 11 inches to get a resolution of around 186 dots per

inch ...