Drawing in GIMP

1. Drawing in GIMP GIMP User Manual

2. 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

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

4. 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

5. 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

6. 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

7. 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

8. 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

9. 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

10. Color Mode Menus • Menu items for color modes: • Image > Mode > RGB • Image > Mode > Grayscale • Image > Mode > Indexed

11. 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

12. Alpha Transparency Menus • Menu items for alpha channel: • Layer > Transparency > Add Alpha Channel • Layer > Transparency > Remove Alpha Channel • Layer > Transparency > Add to Selection

13. 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

14. 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

15. 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

16. 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

17. Pencil Line Drawing

18. 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

19. Change Brushes • Changing a brush type is easy • Just click on the brush icon to bring up the Brushes Panel Click to View

20. Brushes Panel • There are many types of brushes to choose from • Just click to choose a different brush

21. 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

22. 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

23. 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/

24. 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

25. Image made with Adobe Brushes

26. 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

27. 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

28. Pencil Drawing Options • Chose to use color from gradient

29. Special Layer Drawing Modes • Normal • Dissolve • Behind and Color Erase modes needs a top layer with an alpha channel (transparency)

30. 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

31. Aliased or Anti-Aliased Lines PencilLines PaintbrushLines

32. 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

33. 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

34. 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

35. 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

36. 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

37. The Erase Tool

38. 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

39. 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

40. Stroking a Selection • Rectangle selection • Line Width 12 • Line Style was a wood grain Pattern

41. 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

42. 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

43. 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

44. Selection using Fuzzy Select

45. Paths Tool • The Paths Tool allows you to create complex selection known as Bezier Curves • You can edit your curve, add or delete points

46. Paths Tool Example

47. 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

48. 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

49. 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

50. 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