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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

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drawing in gimp

Drawing in GIMP

GIMP User Manual

lesson overview
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
Some Drawing Terminology
  • Dithering
  • Anti-aliasing
  • Haloing
  • Color Modes
  • Alpha Transparency
dithering
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
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
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
  • 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
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
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
Color Mode Menus
  • Menu items for color modes:
    • Image > Mode > RGB
    • Image > Mode > Grayscale
    • Image > Mode > Indexed
alpha transparency
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
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 gimp1
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 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
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
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
brushes
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
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
Brushes Panel
  • There are many types of brushes to choose from
  • Just click to choose a different brush
animated image brushes
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
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
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
  • 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
parametric 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
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
Pencil Drawing Options
  • Chose to use color from gradient
special layer drawing modes
Special Layer Drawing Modes
  • Normal
  • Dissolve
  • Behind and Color Erase modes needs a top layer with an alpha channel (transparency)
fuzzy or smooth lines
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
Aliased or Anti-Aliased Lines

PencilLines

PaintbrushLines

airbrush tool
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
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
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
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
  • TheShape box allows dragging of square to change shape
the eraser tool
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
drawing shapes
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
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
Stroking a Selection
  • Rectangle selection
  • Line Width 12
  • Line Style was a wood grain Pattern
free select with the lasso
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
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
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
paths tool
Paths Tool
  • The Paths Tool allows you to create complex selection known as Bezier Curves
  • You can edit your curve, add or delete points
bucket fill tool
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 will reverse fill type
bucket tool affected area
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
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
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
Gradients
  • The Blend tool is another way to fill areas
  • Set the Opacity or Mode
  • Choose a Gradient
  • Choose a Shape and Offset
gradients1
Gradients
  • With the blend tool selected, mouse down in a selection and drag in the direction you want the gradient to flow
reverse gradient
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
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
Vector Graphics Converted
  • After closing the Gfig editor
  • The vector graphics are converted into raster graphics
  • They have their own layer
modify gfig layer
Modify Gfig Layer
  • The Gfig shapes are now just pixels on a layer
  • They can be selected, transformed and moved
summary
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
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