Figure 13.32. The Paint Tools (Tools menu)
The GIMP Toolbox includes thirteen “brush tools”,
all grouped together at the bottom (in the default arrangement).
Figure 13.33. The Paint Tools (Tools Box)
The feature they all have in common is that all of them are used by moving
the pointer across the image display, creating brush-strokes. Four of them
behave like the intuitive notion of "painting" with a brush. The others
use a brush to modify an image in some way rather than paint on it:
The advantages of using GIMP with a tablet instead of a mouse
probably show up more clearly for brush tools than anywhere else:
the gain in fine control is invaluable. These tools also have
special “Pressure sensitivity” options that are only usable
with a tablet.
In addition to the more common “hands-on” method, it is
possible to apply brush tools in an automated way, by creating a
selection or path and then “stroking” it. You can choose to
stroke with any of the brush tools, including nonstandard ones
such as the Eraser, Smudge tool, etc., and any options you set for
the tool will be applied. See the section on Stroking for more information.
Holding down the Ctrl key has a special effect
on every brush tool . For the Pencil,
Paintbrush, Airbrush, Ink Tool, and Eraser tools, it
switches them into “color picker” mode, so that
clicking on an image pixel causes GIMP's foreground to be set
to the active layer's color at that point (or, for the Eraser,
GIMP's background color). For the Clone tool, the
Ctrl key switches it into a mode where
clicking sets the reference point for copying. For the Convolve
tool, the Ctrl key switches between blur and
sharpen modes; for the Dodge/Burn tool, it switches between
dodging and burning.
Holding down the Shift key has the same effect on all brush tools:
it places the tool into straight line
mode. To create a straight line with any of the brush tools, first
click on the starting point, then
press the Shift key. As long as you hold it down, you will see a
thin line connecting the previously clicked point with the current
pointer location. If you click again, while continuing to hold
down the Shift key, a straight line will be rendered. You can
continue this process to create a series of connected line
Holding down both keys puts the tool into
constrained straight line mode. This
is similar to the effect of the Shift key alone, except
that the orientation of the line is constrained to the
nearest multiple of 15 degrees. Use this if you want to
create perfect horizontal, vertical, or diagonal lines.
Figure 13.34. Tool Options shared by all brush tools
Many tool options are shared by several brush tools: these are described
here. Options that apply onltool-options-brushcommony to one specific
tool, or to a small number of tools, are described in the sections
devoted to those tools.
The Mode drop-down list provides a selection of paint
application modes. As with the opacity, the easiest way to
understand what the Mode setting does is to imagine that the
paint is actually applied to a layer above the layer you are
working on, with the layer combination mode in the Layers
dialog set to the selected mode. You can obtain a great variety
of special effects in this way. The Mode option is only usable
for tools that can be thought of as adding color to the image:
the Pencil, Paintbrush, Airbrush, Ink, and Clone tools. For the
other brush tools, the option appears for the sake of
consistency but is always grayed out. A list of modes can be
found in Section 2, “
In this list, some modes are particular and are described
The Opacity slider sets the transparency level for the brush
operation. To understand how it works, imagine that instead of
altering the active layer, the tool creates a transparent layer
above the active layer and acts on that layer. Changing Opacity in
the Tool Options has the same effect that changing opacity in the
Layers dialog would have in the latter situation. It controls the
of all brush tools, not just those that paint on the active layer.
In the case of the Eraser, this can come across as a bit
confusing: it works out that the higher the “opacity”
is, the more transparency you get.
The brush determines how much of the image is affected by the
tool, and how it is affected, when you trace out a brushstroke
with the pointer. GIMP allows you to use several different types
of brushes, which are described in the
section. The same brush choices are available for all brush tools
except the Ink tool, which uses a unique type of procedurally
generated brush. The colors of a brush only come into play for
tools where they are meaningful: the Pencil, Paintbrush, and
Airbrush tools. For the other brush tools, only the intensity
distribution of a brush is relevant.
This option lets you to modify precisely the size of the brush.
You can use the arrow keys to vary by ±0.01 or the Page-Up and
Page-Down keys to vary by ±0.05. You can obtain the same result if
you have correctly set your mouse-wheel in the Preferences. See
How to vary the
size of a brush
Figure 13.35. The Brush Dynamics check box.
Brush dynamics let you map different brush parameters, commonly at
least size and opacity, to one or more of three input dynamics:
pressure, velocity and random. They are mostly used with tablets,
but Velocity and Random are also usable with a mouse. The
Ink tool, that supported velocity before, has been overhauled and
now handles velocity-dependent painting much better.
A new option has been added in stroking paths. Stoke Path and
Stroke Selection have now a check box for emulating brush
dynamics when you stroke using a paint tool. That means that when
you stoke, brush pressure and velocity are varying along the length
of the stroke. Pressure starts with zero, ramps up to full pressure
and then ramps down again to no pressure. Velocity starts from
zero and ramps up to full speed by the end of the stroke.
The Pressure Sensitivity section is only meaningful if you are
using a tablet: it allows you to decide which aspects of the
tool's action should be affected by how hard you press the stylus
against the tablet. The possibilities are
rate, size, and
color. They work together: you can enable
as many of them as you like.
For each tool, only the ones that are meaningful are listed.
Here is what they do:
The effect of this option is described above.
This option applies to brushes with fuzzy edges. If it is
enabled, the harder you press, the darker the fuzzy parts of
the brush will appear.
This option applies to the Airbrush, Convolve tool, and
Smudge tool, all of which have time-based effects. Pressing
harder makes these tools act more rapidly.
This option applies to all of the pressure sensitive brush
tools. If the option is checked, then pressing harder will
increase the size of the area affected by the brush.
This option only applies to the painting tools: the Pencil,
Paintbrush, and Airbrush; and only if you are using colors
from a gradient. If these conditions are met, then pressing
harder causes colors to be taken from higher in the
This option causes each stroke to fade out over the specified
distance. It is easiest to visual for painting tools, but applies
to all of the brush tools. It is equivalent to gradually reducing
the opacity along the trajectory of the stroke. Note that, if you
are using a tablet, this option does not change the effects of
You know “spacing” in brush strokes: strokes are
made of successive brush marks which, when they are very near,
seem to draw a continuous line. Here, instead of being aligned
brush marks are scattered over a distance you can set with the
Figure 13.36. “Jitter” example
The Incremental check-box activates incremental mode for the tool.
If it is deactivated, the maximum effect of a single stroke is
determined by the opacity, and moving the brush repeatedly over
the same spot will not increase the effect beyond this limit. If
Incremental is active, each additional pass with the brush will
increase the effect, but the opacity can't exceed the opacity set
for the tool. This option is available for all brush tools except
those which have a “rate”
control, which automatically implies an incremental effect. See
also Section 2, “
Color from Gradient
Figure 13.37. Gradient options for painting tools.
Instead of using the foreground color (as shown in the Color Area
of the Toolbox), by checking the "Use color from gradient" option
you can choose to paint with a gradient, giving colors that change
gradually along the brush trajectory. For basic information on
gradients, see the
You have several options to control what gradient is used and how
it is laid out:
Here you see a display of the current gradient. Clicking on
it brings up a Gradient Selector, which will allow you to
choose a different gradient.
Normally a brushstroke starts with colors from the left side
of the gradient, and progresses rightward. If "Reverse" is
checked, the stroke starts with colors from the right side,
and progresses leftward.
This option sets the distance corresponding to one complete
cycle through the gradient colors. The default units are
pixels, but you can choose a different unit from the
adjoining Units menu.
Illustration of the effects of the three gradient-repeat
options, for the “Abstract 2” gradient.
This option determines what happens if a brushstroke extends
farther than the Length specified above. There are three
None means that the color from the end of
the gradient will be used throughout the remainder of the
Sawtooth wave means that the
gradient will be restarted from the beginning, which
will often produce a color discontinuity;
Triangular wave means that the
gradient will be traversed in reverse, afterwards bouncing
back and forth until the end of the brushstroke.
3.1.3. Paint Mode Examples
The following examples demonstrate some of GIMP's
Figure 13.39. Dissolve mode example
For any paint tool with opacity less than 100%, this very
useful mode doesn't draw transparency but determines the
probability of applying paint. This gives nice patterns of
dots to paint-strokes or filling.
Figure 13.40. Painting in Dissolve mode
Figure 13.41. Example for layer mode “Behind”
This mode applies paint only to transparent areas of the
layer: the lower the opacity, the more paint is applied.
Thus, painting opaque areas has no effect; painting
transparent areas has the same effect as normal mode. The
result is always an increase in opacity. Of course none of
this is meaningful for layers that lack an alpha channel.
In the above example image, Wilber is on the top layer,
surrounded by transparency. The lower layer is solid light
blue. The Bucket Fill tool was used, with the
Fill Whole Selection option checked
and the entire layer was selected. A pattern was used to
paint with the Bucket Fill tool.
The next image (below) has two layers. The upper layer is active.
Three brushtrokes with pencil, red color at 100%, 50%, 25%: only
transparent or semi-transparent pixels of the layer are painted.
Figure 13.42. Painting in “Behind” mode
Figure 13.43. Example for layer mode “Color erase”
This mode erases the foreground color, replacing it with
partial transparency. It acts like the
Color to Alpha
filter, applied to the area under the brushstroke. Note that
this only works on layers that possess an alpha channel;
otherwise, this mode is identical to Normal.
In the above example image, the color of the Bucket Fill tool
was white, so white parts of Wilber were erased and the blue
background shows through.
This image below has only one layer, the background layer.
Background color is sky blue. Three brushtrokes with
With the exact color of the blue area: only this blue color is
With the exact color of the red area. Only this red color is
erased, whatever its transparency. Erased areas are made
With the sky blue color of the layer background: only this
color is erased.
Figure 13.44. Painting in “Color Erase” mode
3.1.4. Further Information
Advanced users may be interested to know that brush tools actually
operate at a sub-pixel level, in order to avoid producing jagged-looking
results. One consequence of this is that even if you work with a
hard-edged brush, such as one of the Circle brushes, pixels on the edge
of the brushstroke will only be partially affected. If you need to have
all-or-nothing effects (which may be necessary for getting a good
selection, or for cutting and pasting, or for operating pixel-by-pixel
at a high zoom level), use the Pencil tool, which makes all brushes
perfectly hard and disables sub-pixel anti-aliasing.