Using Masks and Layers—Painting, Filling, and Color Tools - GIMP 2.6 for Photographers: Image Editing with Open Source Software - page 228

The Ofset values will determine the direction of the shadow in relation to
the image object. Positive values for Offset X will place the shadow at the right,
while negative values will place it at the left. Positive values for Offset Y will
place the shadow below the selected object or character, while negative ones
will place the shadow above it. The program defaults are set to mirror morning
light, which comes from the top-left corner. The drop shadow is automatically
created on a new layer, and it can be positioned afterward at will.
To make the shadow appear more natural, you can apply a soft edge to
the borders and set the blur radius (edge sharpness) since shadows normally
don't have hard edges.
The default color for the shadow is black, but you can select any color you
wish to attain the desired effect. For example, if you select a white shadow on
a dark background, the image object would appear to glow.
Real shadows are rarely pitch black and opaque. For a realistic look, you
can move the Opacity slider to give the shadow some transparency.
A drop shadow is larger than the object casting it. For this reason, leave the
box next to Allow resizing checked. The shadow will then grow proportionally
larger than the object casting it.
When you are satisfied with your changes, click OK . The drop shadow
will be automatically generated and inserted as a new, separate layer into the
image.
GIMP is a true ilter workshop. In this topic, you'll be introduced to only a
few of the filters available, so don't be afraid to explore the effects of the filters
on your own. The next section provides descriptions of certain filters along
with tips on how to use them.
Using the Text Tool and Drop Shadow—a Practical Exercise
It's now time to practice what you've learned about the Text tool . And while
you're at it, you can play with some filters and effects, such as the ones
available via the Filters > Light and Shadow > Drop Shadow menu option:
• Open your image bluesky.xcf and save it, using a new name such as
greetingcard.xcf .
• Set the text color (foreground color) you want to use.
• Create some greeting card text, using the default settings. (As you create
the text, keep in mind that you will be painting Easter eggs to add to the
image later on.)
• Modify the text attributes in the Text tool options dialog.
• Choose Filters > Decor > Add Bevel to create a three-dimensional look for
the text. Remember to duplicate the text layer beforehand and to apply
the filter to the copy.
• Choose Filters > Light and Shadow > Drop Shadow . By using the settings
described in the previous section, create a shadow effect for the active,
duplicated layer with text.
• Save your image.