Drawing in GIMP

GIMP User Manual

Lesson Overview Understand how new graphical content can

created by combining free-hand techniques with existing image content

Become familiar with some common graphics terminology: dithering, anti-aliasing, haloing, color modes, and alpha transparency

Learn how to use the basic drawing tools and options of a graphical application like GIMP

Extend the capability of GIMP to create vector like shapes using the Gfig dialog

Some Drawing Terminology Dithering Anti-aliasing Haloing Color Modes Alpha Transparency

Dithering Dithering is a technique used in computer

graphics to create the illusion of more colors when displaying an image which has a low color depth

The missing colors are reproduced by a certain arrangement of pixels in the available colors The human eye perceives this as a mixture

of the individual colors Dithering increases the size of an indexed

formatted image The Gradient Tool in GIMP uses dithering

Dithering and Indexed Format

When converting a GIMP image from RGB format to Indexed Format you may choose dithering to smooth banding effects

Both GIF and PNG formats can use indexed color

Anti-Aliasing When rendering an edge at an angle, it will

look “jagged” because of the nature of pixels

Anti-aliasing tries to make the edges look smoother by giving the boundary pixels a color between the image and the background image

The human eye then blends the two colors on either side

Good for text in graphics Adds to the file size

Haloing

Haloing is undesirable effect that is created when using transparency

Caused because the edges of an anti-aliased object, such as text, are not purely the background color, they have been blurred

When the background is made transparent, these blurred pixels still show up

Preventing Haloing

If possible, set background color to your planned web page background color

If you want transparency in the background, set this before drawing any shapes or text

You can also turn off anti-aliasing for a drawing tool or selection tool

Color Modes in GIMP True Color (RGB)

Millions of colors Grayscale

The grayscale mode uses one channel to display a gray image

Indexed Color The image consist of pixels picked from

a palette of up to 256 colors By converting to this mode you are

reducing the color depth of an image

Color Mode Menus

Menu items for color modes: Image > Mode > RGB Image > Mode > Grayscale Image > Mode > Indexed

Alpha Transparency Regardless of the mode, images can have

an optional alpha channel for transparency By enabled by alpha channel, you can

create a picture by stacking several layers on top of each other, save images for the web, or create images for 3D graphics that have holes or semi-opaque areas

Use GIF as a Web format to supports fully opaque or fully transparent images

Alpha Transparency Menus

Menu items for alpha channel: Layer > Transparency > Add Alpha

Channel Layer > Transparency > Remove Alpha

Channel Layer > Transparency > Add to Selection

Drawing in GIMP Most drawings begin with a blank

canvas Choose the image size and

background color Always create a layer for each figure

in your drawing This allows you to duplicate figures and

change background color if necessary Name each layer for the main figure on

the layer

Drawing Techniques in GIMP Drawing lines and curves Changing colors and brushes Drawing circles, rectangles, and

other shapes Using a filter to draw temporary

vector graphical objects Outlining and filling regions Filling with patterns and gradients

New Image Always start with an existing or a

new image Set the background color or make it

transparent Create a new layer for each

functional unit of your drawing Name the layer with a meaningful

name

Drawing Lines and Curves Use the Pencil tool to create hard-edged lines To draw a free hand line, hold down the left

mouse button and drag the mouse where you want.

To draw a straight line, click the first point, hold down the shift key, then click the last point.

The pencil will have a round point determined by the brush that is selected To turn off the brush size in the cursor, go to

Edit=>Preferences=>Image Window and set Mouse Pointer Pointer Mode to be Tool Icon with crosshair or just crosshair

Pencil Line Drawing

Brushes Changing the brush gives you control

of the width and shape of the lines you draw with any of the GIMP drawing tools

There are several ways to change brushes Click on the brush circle in the toolbox

brush icon or choose to show the brushes panel from the Windows=>Dockable Dialogs=>Brushes menu

Change Brushes

Changing a brush type is easy

Just click on the brush icon to bring up the Brushes Panel Click to

View

Brushes Panel There are

many types of brushes to choose from

Just click to choose a different brush

Animated Image Brushes Some built in animated

image brushes can be selected

You can vary the spacing

The fixed color ignores current foreground or background colors

Importing Abobe Brushes There are many brushes available on

the Internet One standard format that can be

imported into GIMP are Abobe brushes. These are usually available in zipped files The extension are .abr for Adobe brushes

Loading too many brushes will make GIMP take a long time to start

Brusheezy.com – This web site has many Adobe

brushes available with unrestricted use requirements

Download the zipped file Extract the .abr files Place in your GIMP brushes area:

C:/ProgramFiles/GIMP-2.0/share/gimp//2.0/brushes/

Custom Brushes Custom brushes you load can be

drawn like a line or stamped to create an individual image

You can usually size the brush, choose a color, set opacity or other brush attributes

Don’t be afraid to experiment with these custom brushes, you can always undo and try again

Image made with Adobe Brushes

Parametric Brushes Parametric brushes are based on a

mathematical representation of a shape like round, diamond, or square

Use the Brush Editor dialog to create a new brush with the following: Radius Hardness Aspect Ratio Angle Spacing

Drawing Tool Options All the line drawing tools have similar

options: Opacity – percentage of transparency Mode – special drawing modes Fade out – line fades over a distance Incremental- only if opacity is < 100%,

will make a line darker if repeated Use color from gradient – Uses

gradient instead of current foreground color

Pencil Drawing Options

Chose to use color from gradient

Special Layer Drawing Modes

Normal Dissolve Behind and

Color Erase modes needs a top layer with an alpha channel (transparency)

Fuzzy or Smooth Lines? The pencil tool draws hard-edged lines

but has jagged edges Not anti-aliased by default

The paintbrush tool draws fuzzy lines with the brushes These lines are anti-aliased The edges are semi-transparent and are

blended with the background color The paintbrush can also use hard-edged

brushes

Aliased or Anti-Aliased Lines

PencilLines

Paintbrush

Lines

Airbrush Tool

This tool always draws a fuzzy edge, even if a hard-edged brush is selected

The airbrush is time sensitive, the slower you go, the darker it draws The Rate controls how sensitive the tool

is to movement The Pressure controls the darkness.

Think of this as the amount of paint the airbrush is spraying

The Calligraphic Brush This tool mimics a real calligraphic

pen or brush Choose the airbrush tool, then

select a calligraphic brush The path of the line changes

depending of the orientation of the brush

Uses the same options as the airbrush tool, rate and pressure

Ink Pen Tool This tool emulates

an old fashioned fountain pen

Has different shaped nibs or point types

Ignores other brushes

Has its own notion of a brush

The Ink Pen Tool Adjustment controls

the width of the nib and its angle

Sensitivity controls how much ink is released

Type controls shape of nib

The Shape box allows dragging of square to change shape

The Eraser Tool If the current layer has an alpha channel,

the layer supports transparency, then the eraser will work

The eraser uses the current brush to affect its shape

You can zoom to magnify the image to control erasing at the pixel level

Can erase with a hard edge or a soft edge

The Erase Tool

Drawing Shapes

GIMP is not a vector graphic drawing program

The Gfig Filter allows some vector graphic shape drawing capability (More later on this!)

Use a selection tool and then fill or stroke the selection to make your own shapes

Outlining Selections: Stroking

Draw a selection with either the rectangle, ellipse selection tools

Open the Stroke Selection dialog once the selection is active by Edit=>Stroke Selection

Set the Line Width, the Line Style or choose a paint tool if wanted

Then click the Stoke button

Stroking a Selection Rectangle

selection Line Width 12 Line Style was

a wood grain Pattern

Free Select with the Lasso Draw any shape with the Lasso tool You can use the Stoke Selection dialog

to stroke the edge of the selected area Use Edit=>Fill with FG Color to fill the

selection with the current foreground color

You can also fill a selection by dragging the forecolor or background color pattern swatches into the image

Free Select Tool Selection

Create selection using the Free Select Tool (also called Lasso)

Stroke Selection using Paintbrush

Fill color using Fill with FC Color

Fuzzy Selection Tool Also called the

Magic Wand This tool allows

selection based on color similarity

The Threshold option can be used to broaden the selection to touching pixels

Selection using Fuzzy Select

Paths Tool The Paths Tool

allows you to create complex selection known as Bezier Curves

You can edit your curve, add or delete points

Paths Tool Example

Bucket Fill Tool Use this tool for more

complicated color filling Opacity and Mode are

the same as with other tools

Fill Type lets you fill with FG, BG, or Pattern

Holding <Ctrl> will reverse fill type

Bucket Tool – Affected Area

Check to Fill similar colors

The Threshold slides controls just how similar the colors will be

This may take some experimenting to get it right

Patterns A Pattern is just

an image Patterns are usually

tileable, repeatable Use the Pattern

swatch to set the Pattern you want

Patterns can be edited and saved as a new Pattern

Adding New Patterns Create your own pattern and save it with

a .pat extension Find a pattern with a .pat extension such

as those at www.Brusheezy.com Place in your pattern file in this area:

C:/ProgramFiles/GIMP-2.0/share/gimp//2.0/patterns/

Open GIMP again and the pattern should be available

Gradients The Blend tool is

another way to fill areas

Set the Opacity or Mode

Choose a Gradient Choose a Shape and

Offset

Gradients

With the blend tool selected, mouse down in a selection and drag in the direction you want the gradient to flow

Reverse Gradient

Use a selection tool like the lasso to draw the selection

Choose a Gradient and then click the Reverse box

Use your mouse to drag the direction you want

Vector Graphics with Gfig A special filter called Gfig can be

used to create a layer with vector graphics

After drawing your shapes, close the Gfig editor and you will now have a layer in your drawing

You can save your Gfig drawing and reopen it at another time

Go to the Filter=>Render=>Gfig

Vector Graphics Converted After closing

the Gfig editor The vector

graphics are converted into raster graphics

They have their own layer

Modify Gfig Layer

The Gfig shapes are now just pixels on a layer

They can be selected, transformed and moved

Summary

Use the various tools and brushes to create the drawing you want

Fill the shapes and add stroking to control the edges

Use the Gfig filter to draw vector graphic shapes if you need to

You can use these techniques to draw anything you can think of, with patience and a lot of layers