Overview
My haloing technique slightly blurs the shaded relief only behind map labels.
Working in Photoshop, I place a duplicate relief layer below the original and then blur it (right). The top relief layer contains a layer mask. The rasterized type in the mask is widened and feathered, allowing the blurred relief below to selectively show through.
The problem
Map labels are difficult to read when they interact with background shaded relief that is too dark and intricate (above, left). A common solution is to create vector buffers around the type to block out the relief (above, center). But that cure is often worse than the disease—the buffers look harsh and unrefined.
This tutorial describes a technique for creating delicate halos that improve type legibility and blend softly with the background shaded relief (above, right). Sometimes you can have it all.
Procedure
1) To more easily follow along, I recommend downloading the tutorial map linked above of Logan Pass, Glacier National Park, Montana. The download includes an Adobe Illustrator map with type and a Photoshop shaded relief.
2) Copying and pasting type from the Illustrator map into the Photoshop relief while maintaining perfect registration is key to success. First, draw a registration box in Illustrator on a new layer that aligns to the placed Photoshop relief. The box should have no stroke and no fill. Make sure that all labels that you want to halo are inside the box. Be careful that type on paths and stray points are not outside the box. Also, the type should be free of style effects, such as drop shadows and glows.
3) Unlock, select, and copy the contents of the type layers (shown in red and yellow below) and the registration box (shown in black).
4) Open the Photoshop relief. Paste (as pixels) the type and registration box copied from Illustrator. The registration box from Illustrator should precisely align with relief artboard in Photoshop. Double click on the pasted type to commit the transformation. Move the now rasterized type layer above the relief.
5) Duplicate the relief layer. On the lower of the two relief layers, apply Gaussian blur (Filter/Blur/Gaussian Blur) with a radius of 3.
6) Add a layer mask to the top relief layer by clicking the "Add layer mask" button at the bottom of the layers window. The contents of the layer mask will be white
7) Go to the type layer that you pasted in step 4. Select the Magic Wand Tool and enter these settings: Sample size = Point Sample, Tolerance = 0, and turn off the option for sampling only contiguous pixels. Click the Magic Wand in empty part of the type layer. Inverse the selection (Selection/Inverse). The type is now selected.
8) Click on the layer mask on the top relief layer. Expand the type selection by three pixels (Selection/Modify/Expand) and feather the expanded selection by three pixels (Selection/Modify/Feather). Fill with black and deselect the type selection.
9) Turn off or delete the type layer that is no longer needed. The Photoshop file should now have only two relief layers, the blurred relief on the bottom and the original relief with a type layer mask on top. Save the file.
10) Open the Illustrator map. Illustrator should automatically update the placed shaded relief that you just modified and saved in Photoshop. The type is now easier to read because of the blurred shaded relief behind the labels.
You can stop now if you are satisfied with the readability of the labels. However, additional lightening or darkening behind the labels may be needed. Read on to learn how to do this.
10) Creating light halos (for dark labels) and dark halos (for light labels) is most easily done in Adobe Illustrator with drop shadows (Effect/Stylize/Drop Shadow).
Light halos for dark labels: On the tutorial map, select all type on the red layers. Use the drop shadow settings shown below, left.
Dark halos for light labels: On the tutorial map, select all type on the yellow layer. Use the drop shadow settings shown below, right.
Readable labels on a portion of the tutorial map after creating halos, which are barely noticeable.
Comments
- Besides shaded relief, my type haloing technique works well with other background raster art, such as aerial photographs, satellite images, and land cover.
- Depending on the size and resolution of your map, all of the suggested settings in this tutorial may need to be adjusted for best results.
- Symbols associated with map labels, such as peak markers, do not need halos.
- It is also possible to add light and dark type halos in Photoshop. For example, to create light halos, add a Levels adjustment layer above the blurred relief layer. A midpoint setting of 1.2 (see below) is a good place to start.
