Graphics and Java 2D

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Graphics and Java 2D
2
Introduction

• Javas graphics capabilities
• Drawing 2D shapes
• Controlling colors
• Controlling fonts
• Java 2D API
• More sophisticated graphics capabilities
• Drawing custom 2D shapes
• Filling shapes with colors and patterns

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IntroductionClasses and Interfaces
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Introduction

• Javas coordinate system
• Scheme for identifying all points on screen
• Upper-left corner has coordinates (0,0)
• Coordinate point composed of x-coordinate and
  y-coordinate

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Graphics Contexts and Graphics Objects

• Graphics context
• Enables drawing on screen
• Graphics object manages graphics context
• Controls how information is drawn
• Class Graphics is abstract
• Cannot be instantiated
• Contributes to Javas portability
• Class Component method paint takes Graphics
  object
• public void paint( Graphics g )
• Called through method repaint

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Color Control

• Class Color
• Defines methods and constants for manipulating
  colors
• Colors are created from red, green and blue
  components
• RGB values

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Color constant and value
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Color methods color-related Graphic methods
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1 // ShowColors.java 2 // Choosing
colors with JColorChooser. 3 import
java.awt. 4 import java.awt.event. 5
import javax.swing. 6 7 public
class ShowColors extends JFrame 8
private JButton changeColorButton 9
private Color color Color.LIGHT_GRAY 10
private Container container 11 12 //
set up GUI 13 public ShowColors() 14
15 super( "Using JColorChooser" ) 16
17 container getContentPane() 18
container.setLayout( new FlowLayout()
) 19 20 // set up changeColorButton
and register its event handler 21
changeColorButton new JButton( "Change Color"
) 22 changeColorButton.addActionListener
( 23
10
24 new ActionListener() //
anonymous inner class 25 26 //
display JColorChooser when user clicks button 27
public void actionPerformed(
ActionEvent event ) 28 29
color JColorChooser.showDialog(
30 ShowColors.this,
"Choose a color", color ) 31 32
// set default color, if no color is
returned 33 if ( color null
) 34 color
Color.LIGHT_GRAY 35 36 //
change content pane's background color 37
container.setBackground( color ) 38
39 // end anonymous
inner class 40 ) // end call to
addActionListener 41 42
container.add( changeColorButton ) 43 44
setSize( 400, 130 ) 45 setVisible(
true ) 46 // end ShowColor2 constructor

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47 // execute application 48 public
static void main( String args ) 49 50
ShowColors application new
ShowColors() 51 application.setDefaultCl
oseOperation( JFrame.EXIT_ON_CLOSE ) 52
53 // end class ShowColors2
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Font Control

• Class Font
• Contains methods and constants for font control
• Font constructor takes three arguments
• Font name
• Monospaced, SansSerif, Serif, etc.
• Font style
• Font.PLAIN, Font.ITALIC and Font.BOLD
• Font size
• Measured in points (1/72 of inch)

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Font-related methods and constants
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Font-related methods and constants
// set font to Serif (Times), bold, 12pt and
draw a string g.setFont( new Font( "Serif",
Font.BOLD, 12 ) ) g.drawString( "Serif 12
point bold.", 20, 50 ) // set font to
Monospaced (Courier), italic, 24pt and draw a
string g.setFont( new Font( "Monospaced",
Font.ITALIC, 24 ) ) g.drawString(
"Monospaced 24 point italic.", 20, 70 ) //
set font to SansSerif (Helvetica), plain, 14pt
and draw a string g.setFont( new Font(
"SansSerif", Font.PLAIN, 14 ) )
g.drawString( "SansSerif 14 point plain.", 20, 90
) // set font to Serif (Times), bold/italic,
18pt and draw a string g.setColor( Color.RED
) g.setFont( new Font( "Serif", Font.BOLD
Font.ITALIC, 18 ) ) g.drawString(
g.getFont().getName() " " g.getFont().getSize(
) " point bold italic.", 20, 110 )
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Java 2D API

• Java 2D API
• Provides advanced 2D graphics capabilities
• java.awt
• java.awt.image
• java.awt.color
• java.awt.font
• java.awt.geom
• java.awt.print
• java.awt.image.renderable
• Uses class java.awt.Graphics2D
• Extends class java.awt.Graphics

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Java 2D API

• when using Swing overide paintComponent instead
  of paint.

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Java 2D API

• Java 2D shapes
• Package java.awt.geom
• Ellipse2D.Double
• Rectangle2D.Double
• RoundRectangle2D.Double
• Arc3D.Double
• Lines2D.Double

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Java 2D API

• The Java 2D API introduces java.awt.Graphics2D ,
  a new type of Graphics object.
• Graphics2D extends the Graphics class to provide
  access to the enhanced graphics and rendering
  features of the Java 2D API.
• To use Java 2D API features, you cast the
  Graphics object passed into a component's
  rendering method to a Graphics2D object.

public void Paint(Graphics g) Graphics2D g2
(Graphics2D) g ...
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Java 2D Drawing Process Step 1

• Cast Graphics object to Graphics 2D
• public void paintComponent(Graphics g)
• super.paingComponent(g) // Typical Swing
• Graphics2d g2d (Graphics2d) g
• g2d.doSomeStuff(...)
• ...
• Note
• All methods that return Graphics in Java 1.1
  return Graphics2D in Java 2
• paint, paintComponent
• getGraphics

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Java 2D Drawing Process Step 2

• Set pen parameters
• g2d.setPaint(fillColorOrPattern)
• g2d.setStroke(penThicknessOrPattern)
• g2d.setComposite(someAlphaComposite)
• g2d.setFont(someFont)
• g2d.translate(...)
• g2d.rotate(...)
• g2d.scale(...)
• g2d.shear(...)
• g2d.setTransform(someAffineTransform)

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Java 2D Drawing Process Step 3

• Create a Shape object.
• Rectangle2D.Double rect ...
• Ellepse2D.Double ellipse ...
• Polygon poly ...
• GeneralPath path ...
• // satisfies Shape interface
• SomeShapeYouDefined shape ...
• Note
• Most shapes are in the java.awt.geom package
• There is a corresponding Shape class for most of
  the drawXxx methods of Graphics

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Java 2D Drawing Process Step 4

• Draw an outlined or filled version of the Shape
• g2d.draw(someShape)
• g2d.fill(someShape)
• The legacy methods are still supported
• drawString
• drawLine, drawRect, fillRect