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<div class="sect2" lang="en" xml:lang="en">
<div class="titlepage">
<div>
<div>
<h3 class="title"><a id="gimp-brushes"></a>4.8. Brushes</h3>
</div>
</div>
</div>
<a id="id3310507" class="indexterm"></a>
<div class="informalfigure">
<div class="mediaobject">
<img src="../images/using/brush-examples.png" />
<div class="caption">
<p>
A number of examples of brushstrokes painted using different
brushes from the set supplied with GIMP. All were painted
using the Paintbrush tool.
</p>
</div>
</div>
</div>
<p>
A <span class="emphasis"><em>brush</em></span> is a pixmap or set of pixmaps used for
painting. GIMP includes a set of 10 "paint tools, which not
only perform operations that you would think of as painting, but
also operations such as erasing, copying, smudging, lightening or
darkening, etc. All of the paint tools, except the ink tool, use
the same set of brushes. The brush pixmaps represent the
marks that are made by single "touches" of the brush to the image.
A brush stroke, usually made by moving the pointer across the image with
the mouse button held down, produces a series of marks spaced along the
trajectory, in a way specified by the characteristics of the brush
and the paint tool being used.
</p>
<p>
Brushes can be selected by clicking on an icon in the <a href="ch04s10.html" title="10. Brushes dialog">Brushes dialog</a>. GIMP's
<span class="emphasis"><em>current brush</em></span> is shown in the
Brush/Pattern/Gradient area of the Toolbox. Clicking on the brush
symbol there is one way of activating the Brushes dialog.
</p>
<p>
When you install GIMP, it comes presupplied with a number of basic
brushes, plus a few bizarre ones that serve mainly to give you
examples of what is possible (i. e., the "green pepper" brush in
the illustration). You can also create new brushes, or
download them and install them so that GIMP will recognize them.
</p>
<p>
GIMP can use several different types of brushes. All of them,
however, are used in the same way, and for most purposes you don't
need to be aware of the differences when you paint with them.
Here are the available types of brushes:
</p>
<div class="variablelist">
<dl>
<dt>
<span class="term">Ordinary brushes</span>
</dt>
<dd>
<p>
Most of the brushes supplied with GIMP fall into this
category. They are represented in the Brushes dialog by
grayscale pixmaps. When you paint using them, the current
foreground color (as shown in the Color Area of the Toolbox)
is substituted for black, and the pixmap shown in the brushes
dialog represents the mark that the brush makes on the image.
</p>
<p>
To create such a brush:
Create a small image in gray levels using zoom. Save it with the
.gbr extension. Click on Refresh button in the Brush Dialog to get
it in preview without it being necessary to restart GIMP.
</p>
</dd>
<dt>
<span class="term">Color brushes</span>
</dt>
<dd>
<p>
Brushes in this category are represented by colored images in
the Brushes dialog. They can be a text. When you paint with them,
the colors are used as shown; the current foreground color does
not come into play. Otherwise they work the same way as ordinary
brushes.
</p>
<p>
To create such a brush, create a small RGBA image. For this, open
New Image, select RGB for image type and Transparent for fill type.
Draw your image and save it first to .xcf file to keep its
properties. Then save it to .gbr format. Click on
<span class="emphasis"><em>Refresh</em></span> button in Brush Dialog to get your
brush without it being necessary to restart Gimp.
</p>
<div class="tip" style="margin-left: 0.5in; margin-right: 0.5in;">
<table border="0" summary="Tip">
<tr>
<td rowspan="2" align="center" valign="top" width="25">
<img alt="[Tip]" src="../images/tip.png" />
</td>
<th align="left">Tip</th>
</tr>
<tr>
<td colspan="2" align="left" valign="top">
<p>
You can transform a selection to a brush by using the
Selection/To Brush script-fu.
</p>
</td>
</tr>
</table>
</div>
</dd>
<dt>
<span class="term">Image hoses / Image pipes</span>
</dt>
<dd>
<p>
Brushes in this category can make more than one kind of mark
on an image. They are indicated by small red triangles at th
lower right corner of the brush symbol in the Brushes dialog.
They are sometimes called "animated brushes"
because the marks change as you trace out a brushstroke. In
principle, image hose brushes can be very sophisticated,
especially if you use a tablet, changing shape as a function
of pressure, angle, etc. These possibilities have never
really been exploited, however; and the ones supplied with
GIMP are relatively simple (but still quite useful).
</p>
</dd>
<dt>
<span class="term">Parametric brushes</span>
</dt>
<dd>
<p>
These are brushes created using the <a href="ch04s10.html#gimp-brush-editor-dialog" title="Brush Editor">Brush Editor</a>, which
allows you to generate a wide variety of brush shapes by
using a simple graphical interface. A nice feature of
parametric brushes is that they are
<span class="emphasis"><em>resizable</em></span>. In GIMP 2.2, it is possible,
using the Preferences dialog, to make key presses or mouse
wheel rotations cause the current brush to become larger or
smaller, if it is a parametric brush.
</p>
</dd>
</dl>
</div>
<p>
One category that GIMP does not have is full-fledged
<span class="emphasis"><em>procedural</em></span> brushes: brushes whose marks are
calculated procedurally, instead of being taken from a fixed
pixmap. (Actually this is not quite correct: the Ink tool uses a
procedural brush, but it is the only one available in GIMP.) A
more extensive implementation of procedural brushes is a goal of
future development for GIMP.
</p>
<p>
In addition to the brush pixmap, each GIMP brush has one other
important property: the brush <span class="emphasis"><em>Spacing</em></span>. This
represents the distance between consecutive brush-marks when a
continuous brushstroke is painted. Each brush has an assigned
default value for this, which can be modified using the Brushes
dialog.
</p>
<div class="simplesect" lang="en" xml:lang="en">
<div class="titlepage">
<div>
<div>
<h4 class="title"><a id="id3310476"></a>Adding New Brushes</h4>
</div>
</div>
</div>
<p>
To add a new brush, after either creating it or downloading it, so
that it shows up in the Brushes dialog, you need to save it in a
format GIMP can use, in a folder included in GIMP's brush search path,
then to <span class="emphasis"><em>Refresh</em></span> the Brush Dialog (or re-start
GIMP). GIMP uses three file formats for brushes:
</p>
<div class="variablelist">
<dl>
<dt>
<span class="term">GBR</span>
</dt>
<dd>
<p>
The <tt class="filename">.gbr</tt> ("<span class="emphasis"><em>g</em></span>imp
<span class="emphasis"><em>br</em></span>ush") format is used for ordinary and
color brushes. You can convert many other types of images,
including many brushes used by other programs, into GIMP
brushes by opening them in GIMP and saving them with file
names ending in <tt class="filename">.gbr</tt>. This brings up a
dialog box in which you can set the default Spacing for the
brush. A more complete description of the GBR file format
can be found in the file <tt class="filename">gbr.txt</tt> in the
<tt class="filename">devel-docs</tt> directory of the GIMP source
distribution.
</p>
</dd>
<dt>
<span class="term">GIH</span>
</dt>
<dd>
<p>
The <tt class="filename">.gih</tt> ("<span class="emphasis"><em>g</em></span>imp
<span class="emphasis"><em>i</em></span>mage <span class="emphasis"><em>h</em></span>ose")
format is used for animated brushes. These brushes are
constructed from images containing multiple layers: each
layer may contain multiple brush-shapes, arranged in a
grid. When you save an image as a <tt class="filename">.gih</tt>
file, a dialog comes up that allows you to describe the
format of the brush. The GIH format is rather complicated:
a complete description can be found in the
file <tt class="filename">gih.txt</tt> in the
<tt class="filename">devel-docs</tt> directory of the GIMP source
distribution. See
<a href="ch02s04s08.html#gimp-GIH-dialog" title="The GIH dialog box">The GIH dialog box</a>
</p>
</dd>
<dt>
<span class="term">VBR</span>
</dt>
<dd>
<p>
The <tt class="filename">.vbr</tt> format is used for parametric
brushes, i. e., brushes created using the Brush Editor.
There is really no other meaningful way of obtaining files
in this format.
</p>
</dd>
</dl>
</div>
<p>
To make a brush available, place it in one of the folders in
GIMP's brush search path. By default, the brush search path
includes two folders, the system <tt class="filename">brushes</tt>
folder, which you should not use or alter, and the
<tt class="filename">brushes</tt> folder inside your personal GIMP
directory. You can add new folders to the brush search path
using the <a href="ch04s18s16.html" title="18.16. Data Folders">Brush
Folders</a> page of the Preferences dialog. Any GBR, GIH, or
VBR file included in a folder in the brush search path will show
up in the Brushes dialog the next time you start GIMP, or as soon
as you press the Refresh button in the Brushes dialog.
</p>
<div class="note" style="margin-left: 0.5in; margin-right: 0.5in;">
<table border="0" summary="Note">
<tr>
<td rowspan="2" align="center" valign="top" width="25">
<img alt="[Note]" src="../images/note.png" />
</td>
<th align="left">Note</th>
</tr>
<tr>
<td colspan="2" align="left" valign="top">
<p>
When you create a new parametric brush using the Brush Editor, it
is automatically saved in your personal
<tt class="filename">brushes</tt> folder.
</p>
</td>
</tr>
</table>
</div>
<p>
There are a number of web sites with downloadable collections of
GIMP brushes. Rather than supplying a list of links that will
soon be out of date, the best advice is to do a Google search for
"Gimp brushes". There are also many collections of brushes for
other programs with painting functionality. Some can be converted
easily into GIMP brushes, some require special conversion
utilities, and some cannot be converted at all. Most fancy
procedural brush types fall into the last category. If you need
to know, look around on the web, and if you don't find anything,
look for an expert to ask.
</p>
</div>
<div class="simplesect" lang="en" xml:lang="en">
<div class="titlepage">
<div>
<div>
<h4 class="title"><a id="gimp-GIH-dialog"></a>The GIH dialog box</h4>
</div>
</div>
</div>
<p>
This dialog box has several options not easy to understand. They
allow you to determine the way your brush is animated.
</p>
<div class="variablelist">
<dl>
<dt>
<span class="term">Spacing (Percent)</span>
</dt>
<dd>
<p>
"Spacing" is the distance between consecutive brush marks when you
trace out a brushstroke with the pointer. You must consider
drawing with a brush, whatever the paint tool, like stamping. If
Spacing is low, stamps will be very close and stroke look
continuous. If spacing is high, stamps will be separated: that's
interesting with a color brush (like "green pepper" for instance).
Value varies from 1 to 200 and this percentage refers to brush
"diameter": 100% is one diameter.
</p>
</dd>
<dt>
<span class="term">Description</span>
</dt>
<dd>
<p>
It's the brush name that will appear at the top of Brush Dialog
(grid mode) when the brush is selected.
</p>
</dd>
<dt>
<span class="term">Cell Size</span>
</dt>
<dd>
<p>
That's size of cells you will cut up in layers... Default
is one cell per layer and size is that of the layer. Then there is
only one brush aspect per layer
</p>
<p>
We could have only one big layer and cut up in it the cells that
will be used for the different aspects of the animated brush.
</p>
<p>
For instance, we want a 100x100 pixels brush with 8 different
aspects. We can take these 8 aspects from a 400x200 pixels layer, or
from a 300x300 pixels layer but with one cell unused.
</p>
</dd>
<dt>
<span class="term">Number of cells</span>
</dt>
<dd>
<p>
That's the number of cells (one cell per aspect) that will be cut in
every layer. Default is the number of layers as there is only one
layer per aspect.
</p>
</dd>
<dt>
<span class="term">Display as:</span>
</dt>
<dd>
<p>
This tells how cells have been arranged in layers. If, for example,
you have placed height cells at the rate of two cells per layer on
four layers, GIMP will display: "1 rows of 2 columns on each layer".
</p>
</dd>
<dt>
<span class="term">Dimension, Ranks, Selection</span>
</dt>
<dd>
<p>
There things are getting complicated! Explanations are necessary to
understand how to arrange cell and layers.
</p>
<p>
GIMP starts retrieving cells from each layer and stacks them into a
FIFO stack (First In First Out: the first in is at the top of the
stack and so can be first out). In our example 4 layers with 2 cells
in each, we'll have, from top to bottom: first cell of first layer,
second cell of first layer, first cell of second layer, second cell
of second layer..., second cell of fourth layer. With one cell per
layer or with several cells per layer, result is the same. You can
see this stack in the Layer Dialog of the resulting .gih image file.
</p>
<p>
Then GIMP creates a computer array from this stack with the
<span class="guilabel">Dimensions</span> you have set. You can use four
dimensions.
</p>
<p>
In computer science an array has a "myarray(x,y,z)" form for a 3
dimensions array (3D). It's easy to imagine a 2D array: on a paper
it's an array with rows and columns
</p>
<div class="mediaobject">
<img src="../images/using/array2D.png" />
</div>
<p>
With a 3d array we don't talk rows and columns but
<span class="guilabel">Dimensions</span> and <span class="guilabel">Ranks</span>. The
first dimension is along x axis, the second dimension along y axis,
the third along z axis. Each dimension has ranks of cells.
</p>
<div class="mediaobject">
<img src="../images/using/array3D.png" />
</div>
<p>
</p>
<p>
To fill up this array, GIMP starts retrieving cells from the top of
stack. The way it fills the array reminds that of an odometer: right
rank digits turn first and, when they reach their maximum, left rank
digits start running. If you have some memories of Basic programming
you will have, with an array(4,2,2), the following succession:
(1,1,1),(1,1,2),(1,2,1),(1,2,2),(2,1,1),(2,1,2),(2,2,2),(3,1,1)....
(4,2,2). We will see this later in an example.
</p>
<p>
Besides the rank number that you can give to each dimension, you can
also give them a <span class="guilabel">Selection</span> mode. You have
several modes that will be applyed when drawing:
</p>
<div class="itemizedlist">
<ul type="disc">
<li>
<p>
<span class="emphasis"><em>Incremental</em></span>: GIMP selects a rank from the
concerned dimension according to the order ranks have in that
dimension
</p>
</li>
<li>
<p>
<span class="emphasis"><em>Random</em></span>: GIMP selects a rank at random
from the concerned dimension.
</p>
</li>
<li>
<p>
<span class="emphasis"><em>Angular</em></span>: GIMP selects a rank in the
concerned dimension according to the moving angle of the brush.
</p>
<p>
The first rank is for the direction 0°, upwards. The other
ranks are affected, counter clockwise, to an angle whose value
is 360/number of ranks. So, with 4 ranks in the concerned
dimension, the angle will move 90° counterclockwise for each
direction change: second rank will be affected to 270° (-90°)
(leftwards), third rank to 180° (downwards) and fourth rank to
90° (rightwards).
</p>
</li>
<li>
<p>
<span class="emphasis"><em>Speed</em></span>,
<span class="emphasis"><em>Pressure</em></span>,
<span class="emphasis"><em>x tilt</em></span> and
<span class="emphasis"><em>y tilt</em></span> are options for sophisticated
drawing tablets.
</p>
</li>
</ul>
</div>
<p>
</p>
</dd>
</dl>
</div>
<div class="variablelist">
<p class="title">
<b>Examples</b>
</p>
<dl>
<dt>
<span class="term">A one dimension image pipe</span>
</dt>
<dd>
<p>
Well! What is all this useful for? We'll see that gradually with
examples. You can actually place in each dimension cases that will
give your brush a particular action.
</p>
<p>
Let us start with a 1D brush which will allow us to study selection
modes action. We can imagine it like this:
</p>
<div class="mediaobject">
<img src="../images/using/array1D.png" />
</div>
<p>
Follow these steps:
</p>
<div class="orderedlist">
<ol type="1">
<li>
<p>
Open a new 30x30 pixels image, RGB with Transparent fill type.
Using the Text tool create 4 layers "1", "2", "3", "4". Delete
the "background" layer.
</p>
</li>
<li>
<p>
Save this image first with .xcf extension to keep its
properties then save it as .gih.
</p>
<p>
The Save As Dialog is opened: select a destination for your
image. OK. The GIH dialog is opened:
Choose Spacing 100, give a name in Description box, 30x30 for
Cell Size, 1 dimension, 1 rank and choose "Incremental" in
Selection box. OK.
</p>
<p>
You may have difficulties to save directly in the GIMP Brush
directory. In that case, save the .gih file manually into the
/usr/share/gimp/gimp 2.0/brushes directory. Then come back
into the Toolbox, clic on the brush icon to open the Brush
Dialog then click on "Refresh". Your new brush appears in the
Brush window. Select it. Select pencil tool for instance and
click and hold with it on a new image
</p>
<div class="mediaobject">
<img src="../images/using/1234incr.png" />
</div>
<p>
You see 1, 2, 3, 4 digits following one another in order.
</p>
<p>
Take your .xcf image file back and save it as .gih setting
Selection to "Random": digits will be displayed at random
order:
</p>
<div class="mediaobject">
<img src="../images/using/1234rand.png" />
</div>
<p>
</p>
<p>
Now select "Angular" Selection:
</p>
<div class="mediaobject">
<img src="../images/using/1234angl.png" />
</div>
<p>
</p>
</li>
</ol>
</div>
<p>
</p>
</dd>
<dt>
<span class="term">A 3 dimensions image hose</span>
</dt>
<dd>
<p>
We are now going to create a 3D animated brush: its orientation will
vary according to brush direction, it will alternate Left/Right
hands regularly and its color will vary at random between black and
blue.
</p>
<p>
The first question we have to answer to is the number of images that
is necessary. We reserve the first dimension (x) to the brush
direction (4 directions). The second dimension (y) is for Left/Right
alternation and the third dimension (z) for color variation. Such a
brush is represented in a 3D array "myarray(4,2,2)":
</p>
<div class="mediaobject">
<img src="../images/using/3Dnum.png" />
</div>
<p>
There are 4 ranks in first dimension (x), 2 ranks in second
dimension (y) and 2 ranks in third dimension (z). We see that there
are 4x2x2 = 16 cells. We need 16 images.
</p>
<div class="orderedlist">
<ol type="1">
<li>
<p>
<span class="emphasis"><em>Creating images of dimension 1 (x)</em></span>:
Open a new 30x30 pixels image, RGB with Transparent Fill Type.
Using the zoom draw a left hand with fingers upwards. Save it as
handL0k.xcf (hand Left O° Black).
</p>
<p>
Open the Layer Dialog. Double click on the layer to open the
Layer Attributes Dialog and rename it to handL0k.
</p>
<p>
Duplicate the layer. Let visible only the duplicated layer,
select it and apply a 90° rotation (Layer/Transform/ 90°
rotation counter-clockwise). Rename it to handL-90k.
</p>
<p>
Repeat the same operations to create handL180k and handL90k.
</p>
</li>
<li>
<p>
<span class="emphasis"><em>Creating images of dimension 2 (y)</em></span>:
This dimension in our example has two ranks, one for left hand
and the other for right hand. The left hand rank exists yet. We
shall build right hand images by flipping it horisontally.
</p>
<p>
Duplicate the handL0k layer. Let it visible only and select it.
Rename it to handR0K. Apply Layer/Transform/Flip Horizontally.
</p>
<p>
Repeat the same operation on the other left hand layers to
create their right hand equivalent.
</p>
<p>
Re-order layers to have a counter-clockwise rotation from top to
bottom, alternating Left and Right: handL0k, handR0k, handL-90k,
handR-90k, ..., handR90k.
</p>
</li>
<li>
<p>
<span class="emphasis"><em>Creating images of dimension 3 (z)</em></span>:
The third dimension has two ranks, one for black color and the
other for blue color. The first rank, black, exists yet. We well
see that images of dimension 3 will be a copy, in blue, of the
images of dimension 2. So we will have our 16 images. But a row
of 16 layers is not easy to manage: we will use layers with two
images.
</p>
<p>
Select the handL0k layer and let it visible only. Using
Image/Canvas Size change canvas size to 60x30 pixels.
</p>
<p>
Duplicate hand0k layer. On the copy, fill the hand with blue
using Bucket Fill tool.
</p>
<p>
Now, select the Move tool. Double click on it to accede to its
properties: check "Move the Current Layer" option. Move the blue
hand into the right part of the layer precisely with the help of
Zoom.
</p>
<p>
Make sure only handL0k and its blue copy are visible. Right click
on the Layer Dialog: Apply the "Merge Visible Layers" command
with the option "Expand as Necessary". You get a 60x30 pixels
layer with the black hand on the left and the blue hand on the
right. Rename it to "handL0".
</p>
<p>
Repeat the same operations on the other layers.
</p>
</li>
<li>
<p>
<span class="emphasis"><em>Set layers in order</em></span>: Layers must be set in
order so that GIMP can find the required image at some point
of using the brush. Our layers are yet in order but we must
understand more generally how to have them in order.There are
two ways to imagine this setting in order. The first method is
mathematical: GIMP divides the 16 layers first by 4; that gives
4 groups of 4 layers for the first dimension. Each group
represents a direction of the brush. Then, it divides each group
by 2; that gives 8 groups of 2 layers for the second dimension:
each group represents a L/R alternation. Then another division
by 2 for the third dimension to represent a color at random
between black and blue.
</p>
<p>
The other method is visual, by using the array representation.
Correlation between two methods is represented in next image:
</p>
<div class="mediaobject">
<img src="../images/using/correlation-en.png" />
</div>
<p>
</p>
</li>
<li>
<p>
Voilà. Your brush is ready. Save it as .xcf first then as .gih
with the following parameters:
Spacing:100 Description:Hands Cell Size: 30x30
Number of cells:16 Dimensions: 3
</p>
<div class="itemizedlist">
<ul type="disc">
<li>
<p>
Dimension 1: 4 ranks Selection: Angular
</p>
</li>
<li>
<p>
Dimension 2: 2 ranks Selection: Incremental
</p>
</li>
<li>
<p>
Dimension 3: 2 ranks Sélection: Random
</p>
</li>
</ul>
</div>
<p>
</p>
<p>
Place your .gih file into GIMP brush directory and refresh the
brush box. You can now use your brush. Unfortunately GIMP 2.0 is
bug-ridden and you may have some difficulties with brush
orientation.
</p>
<p>
Here is the result by stroking an elliptical selection with the
brush:
</p>
<div class="mediaobject">
<img src="../images/using/hands_stroke.png" />
</div>
<p>
</p>
</li>
</ol>
</div>
</dd>
</dl>
</div>
</div>
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