Script-Fu is what the Windows world would call "macros" But
Script-Fu is more powerful than that. Script-Fu is based on an
interpreting language called Scheme, and works by using querying
functions to the Gimp database. You can do all kinds of things
with Script-Fu, but an ordinary Gimp user will probably use it
for automating things that:
You want to do frequently.
Are really complicated to do, and hard to remember.
Remember that you can do a whole lot with Script-Fu. The
scripts that come with Gimp can be quite useful, but they can
also serve as models for learning Script-Fu, or at least as a
framework and source of modification when you make your own
script. Read the Script-Fu Tutorial in the next section
if you want to learn more about how to make scripts.
We will describe some of the most useful scripts in this
chapter, but we won't cover them all. There are simply too many
scripts. Some of the scripts are also very simple and you will
probably not need any documentation to be able to use them.
Script-Fu (a dialect of Scheme) isn't the only scripting
language available for Gimp. But Script-Fu is the only scripting
language that is installed by default. Other available scripting
extensions are Perl and Tcl. You can download and install both
extensions at the Gimp
Plugin Registry.
Installing Script-Fus
One of the great things about Script-Fu is that you can share your
script with all your Gimp friends. There are many scripts
that come with Gimp by default, but there are also vast
quantities of scripts that are available for download all around
the Internet.
If you have downloaded a script, copy or move it to your
scripts directory. It can be found in the Preferences:
Folders → Scripts.
Do a refresh by using
Exts → Script-Fu → Refresh Scripts
from the toolbox.
The script will now appear in one of your menus.
If you don't find it, look for it under the root file menu
filters. If it doesn't appear at all, something was wrong with
the script (e.g. it contains syntax errors).
Do's and Don'ts
A common error when you are dealing with Script-Fus is that you
simply bring them up and press the OK button. When nothing
happens, you probably think that the script is broken or buggy,
but there is most likely nothing wrong with it.
Think again. Did you really read the information in the dialog,
or did you just press the button? If you forgot an input the
script needs, or if you gave it the wrong input, the script will
fail. One of the most common errors is that the font specified
in the script dialog hasn't been installed on your system. So
please check the information in the dialog before blaming the
script.
Different Kinds Of Script-Fus
There are two kinds of Script-Fus -- standalone scripts and
image-dependent scripts. You will find the standalone variants
under
Xtns → Script-Fu → Type of Script in the main toolbox menu,
and the image-dependent scripts are placed under
Script-Fu → Type of Script in the image menu.
Standalone Scripts
We will not try to describe every script in depth. Most
Script-Fus are very easy to understand and use. At the time of
this writing, the following types are installed by default:
Patterns
Web page themes
Logos
Buttons
Utils
Make Brush
Misc.
Patterns
You will find all kinds of pattern-generating scripts
here. Generally, they are quite useful because you can add many
arguments to your own patterns.
We'll take a look at the Land script. In this script you have to
set the image/pattern size, and specify what levels of random to
use for your land creation. The colors used to generate the land
map are taken from the currently selected gradient in the
gradient editor. You must also supply values for the level of
detail, land and sea height/depth and the scale. Scale refers to
the scale of your map, just as in an ordinary road map, 1:10
will be typed as 10.
Web Page Themes
Here is clearly a practical use for scripts. By creating a
script for making custom text, logos, buttons arrows, etc., for
your web site, you will give them all the same style and
shape. You will also be saving a lot of time, because you don't
have to create every logo, text or button by hand.
You will find the Gimp.org theme under the Web page theme
submenu. If you want to create your own theme, this script
will serve as an excellent template that you can modify to
create a theme for your web site.
Most of the scripts are quite self-explanatory, but here are
some hints:
Leave all strange characters like ' and " intact.
Make sure that the pattern specified in the script exists.
Padding refers to the amount of space around your text.
A high value for bevel width gives the illusion of a higher button.
If you type TRUE for "Press", the button will look pushed down.
Choose transparency if you don't want a solid background. If
you choose a solid background, make sure it is the same
color as the web page background.
Logos
Here you will find all kinds of logo-generating scripts. This
is nice, but use it with care, as people might recognize your
logo as being made by a known Gimp script. You should rather
regard it as a base that you can modify to fit your needs. The
dialog for making a logo is more or less the same for all such
scripts:
In the Text String field, type your logo name, like Frozenriver.
In the Font Size text field, type the size of your logo in pixels.
In the Font text field, type the name of the font that you
want to use for your logo.
To choose the color of your logo, just click on the color
button. This brings up a color dialog.
If you look at the current command field, you can watch the
script run.
Make Buttons
Under this headline you'll find a script that makes beveled
buttons. The script has a dozen parameters or so, and most of
them are similar to those in the logo scripts. You can
experiment with different settings to come up with a button you
like.
Utils
Under Utils you will find a small but nice script: the Fontmap
script, which makes an image of your fonts. You will have to
type the names of the fonts you want displayed in the Fonts
text field.
The Custom gradient script creates an image of the current
custom gradient in the gradient editor. This can be useful if
you want to pick colors from a gradient as in a palette.
Misc.
Under Misc. you'll find scripts that can be quite useful, but
aren't suitable for the other submenus. An example is the Sphere
script. You will have to set the radius in pixels to determine
the sphere size. The lighting angle is where at the sphere you
point the spotlight. This value also has an impact on the sphere
shadow. If you don't want a shadow, you will have to type
FALSE. The last thing you have to select is background color,
and the color of your sphere.
Make Brush
This script lets you make your own custom rectangular/circular
brushes, with or without feathered (blurred) edges. The script
will automatically store your brush in your personal brush
directory. You just have to press refresh in the Brush
Selection dialog to use your newly created brush.
Image-Dependent Scripts
These are scripts that perform operations on an existing
image. In many ways they are like the plug-ins in the Filters
menu. The following script groups are installed by default:
Decor
Modify
Animators
Stencil Ops
Alchemy
Shadow
Render
Utils
Selection
Stencil Ops
Here, you'll find two scripts: Carve-It and Chrome-It, which
can render some truly nice artistic effects on grayscale
images.
Drop Shadow
Drop Shadow will cast a shadow behind your selected
object. It has three important parameters. X and Y offset
determine where the shadow will be placed in relation to the
selected object. Offset is measured in pixels. High values
make the shadow look like it's far away, and low values will
make it look closer to the object. The blur value is also
important, because a shadow that is cast far from the object
has a higher blur level.
Perspective Shadow
Perspective Shadow has a very important parameter: the
perspective angle. If this angle is set to 0 or 180, there
will be no shadow, because the script assumes that the object
has no thickness. This also means that this script looks fine
in certain angles, but unnatural in others. The other
parameters are quite self-explanatory. You'll get more blur if
the horizon is far away, and the shadow length is the length
in relation to the selected object.
