TCSS 305 Stepp

1
TCSS 305 (Stepp)

• 2D Graphics
• Horstmann Ch. 7 pp. 258-283
• Java Tutorial Java 2D Graphics.http//java.sun.c
  om/docs/books/tutorial/2d/

2
Outline

• drawing custom shapes and pictures on the screen
• using panels as drawing surfaces (instead of as
  containers)
• fonts, images, and other graphical items

3
A drawing panel

• extend JPanel and override paintComponent method
  to use a panel as a drawing surface
• public void paintComponent(Graphics g)
• coordinate system (0, 0) at top-left,x-axis
  increases rightward, y-axis downward
• panel surface is transparent unless drawn on

4
Some details

• JPanel's paintComponent does important things
  that we don't want to lose, so call the method
  super.paintComponent first thing!
• paintComponent's Graphics g argument represents
  "graphical context" object that can be told to
  draw things on the panel
• Guaranteed for every JPanel that actual object
  passed in is a Graphics2D (can cast)
• panel has small preferred size, so it will be
  tiny when put into some layouts use
  setPreferredSize(Dimension) to make it bigger!
• refreshing panel can't call paintComponent, so
  call repaint()

5
Basic panel painting syntax

• public class MyPanel extends JPanel
• public void paintComponent(Graphics g)
• super.paintComponent(g) // important!
• Graphics2D g2 (Graphics2D) g
• // put your painting code here

6
Quick drawing example

• public class MyPanel extends JPanel
• public MyPanel()
• this.setBackground(Color.WHITE)
• public void paintComponent(Graphics g)
• super.paintComponent(g)
• Graphics2D g2 (Graphics2D) g
• Shape shape new Ellipse2D.Double(10,
  10, 20, 50)
• g2.setPaint(Color.BLUE)
• g2.fill(shape)

7
Drawing text strings

• Graphics2D
• public void drawString(String s, int x, int
  y)Draws given string with its first letter's
  bottom-left corner at the given location.
• The string is drawn using the Graphics2D's
  current color and font settings.
• Before drawing the string, you can set the font,
  color, and other attributes.(see next slides)

8
Fonts

• Graphics2D
• public void setFont(Font f)Sets this Graphics
  context to start writing text in the given font.
  (Forgotten at end of paintComponent call!)
• java.awt.Font
• Text styles used when drawing Strings on the
  panel
• public Font(String name, int style, int size)
• some predefined font names
• "Serif", "SansSerif", "Monospaced"
• font styles (can be combined with operator)
• Font.BOLD
• Font.ITALIC
• Font.PLAIN

9
Colors and paints

• java.awt.Color(a simple single-colored paint)
• public Color(int r, int g, int b)
• public Color(int r, int g, int b, int alpha)
• a partially-transparent color (range 0-255,
  0transparent)
• public Color brighter(), darker()
• public static Color black, blue, cyan, darkGray,
  gray, green, lightGray, magenta, orange, pink,
  red, white, yellow
• java.awt.GradientPaint(smooth transition between
  2 colors)
• public GradientPaint(float x1, float y1, Color
  color1, float x2, float y2, Color color2)
• java.awt.TexturePaint(use an image as a "paint"
  background)

10
Shapes (old style)

• Graphics2D
• public void drawLine(int x1, int y1, int x2, int
  y2)
• public void drawOval(int x, int y, int w, int h)
• public void fillOval(int x, int y, int w, int h)
• public void drawPolygon(int xpoints, int
  ypoints, int len)
• public void fillPolygon(int xpoints, int
  ypoints, int len)
• public void drawRect(int x, int y, int w, int h)
• public void fillRect(int x, int y, int w, int h)
• public void drawArc(...)
• public void fillArc(...)
• ...
• Drawing methods for drawing various lines and
  shapes on a Graphics context. Not recommended to
  be used
• replaced by draw(Shape), fill(Shape) in
  Graphics2D

11
Graphics2D shape methods

• public void draw(Shape s)Draws the outline of
  the given shape using this Graphics2D's current
  pen.
• public void fill(Shape s)Draws outline and fills
  inside of given shape.
• rotate, scale, translate, shear,
  transformPerform various coordinate
  transformations on the Graphics2D context.

12
Shapes (in package java.awt.geom)

• Arc2D.Double(double x, double y, double w,
  double h, double start,
  double extent, int type)An arc, which is a
  portion of an ellipse.
• Ellipse2D.Double(double x, double y,
  double w, double h)An ellipse, which is a
  generalization of a circle.
• Line2D.Double(double x1, double y1, double x2,
  double y2)Line2D.Double(Point p1,
  Point p2)A line between two points.

13
Shapes

• Rectangle2D.Double(double x, double y,
  double w, double h)A rectangle, which is
  a generalization of a square.
• RoundRectangle2D.Double( double x, double y,
  double w, double h, double arcx, double arcy)A
  rounded rectangle.
• GeneralPath()A customizable polygon.

14
Methods of to all shapes

• public boolean contains(double x, double
  y)public boolean contains(Point2D p)
• Whether the given point is contained inside the
  bounds of this shape.
• public Rectangle getBounds()
• A rectangle representing the bounding box around
  this shape.
• public double getCenterX() / getCenterY()
• public double getMinX() / getMinY()
• public double getMaxX() / getMaxY()
• Various corner or center coordinates within the
  shape.
• public boolean intersects(double x, double y,
  double w, double h)
• public boolean intersects(Rectangle2D r)
• Whether this shape touches the given rectangular
  region.

15
Strokes (pen styles)

• Graphics2D
• public void setStroke(Stroke s)Sets type of
  drawing pen (color, width, style)that will be
  used by this Graphics2D.
• java.awt.BasicStroke
• A pen stroke for drawing outlines
• public BasicStroke(float width)
• public BasicStroke(float width, int cap,
  int join)
• public BasicStroke(float width, int cap, int
  join, float miterlimit, float dash, float
  dash_phase)
• cap CAP_BUTT, CAP_ROUND, CAP_SQUARE
• join JOIN_BEVEL, JOIN_MITER, JOIN_ROUND

16
Drawing example 1

• public void paintComponent(Graphics g)
• super.paintComponent(g)
• Graphics2D g2 (Graphics2D) g
• g2.fill(new Rectangle2D.Double(10, 30, 60,
  35))
• g2.fill(new Ellipse2D.Double(80, 40, 50,
  70))

17
Drawing example 2

• public void paintComponent(Graphics g)
• super.paintComponent(g)
• Graphics2D g2 (Graphics2D) g
• g2.setPaint(Color.BLACK)
• g2.fill(new Rectangle2D.Double(10, 30, 100,
  50))
• g2.setPaint(Color.RED)
• g2.fill(new Ellipse2D.Double(20, 70, 20,
  20))
• g2.fill(new Ellipse2D.Double(80, 70, 20,
  20))
• g2.setPaint(Color.CYAN)
• g2.fill(new Rectangle2D.Double(80, 40, 30,
  20))

18
Drawing example 3

• public void paintComponent(Graphics g)
• super.paintComponent(g)
• Graphics2D g2 (Graphics2D) g
• g2.setPaint(Color.BLUE)
• for (int i 1 i lt 10 i)
• g2.fill(new Ellipse2D.Double(15 i, 15
  i, 30, 30))
• g2.setPaint(Color.MAGENTA)
• for (int i 1 i lt 10 i)
• g2.fill(new Ellipse2D.Double(15 (11 -
  i), 15 i,
• 30, 30)

19
Drawing images

• Graphics2D
• public void drawImage(Image i, int x, int y,
  ImageObserver io)
• public void drawImage(Image i, int x, int y, int
  width, int height,
  ImageObserver io)Draws given image object on
  this Graphics context with its top-left corner at
  given location (pass the panel as the
  ImageObserver).

20
Classes for imaging

• java.awt.ToolkitGets images from disk or
  internet
• public static Toolkit getDefaultToolkit()
• public Image getImage(String filename)
• public Image getImage(URL address)
• java.awt.MediaTrackerEnsures that images are
  loaded fully
• public MediaTracker(Component comp)
• public void addImage(Image img, int id)
• public void waitForAll() throws
  InterruptedException
• java.awt.ImageRepresents a graphic image (BMP,
  GIF, ...)
• public int getWidth(ImageObserver obs)
• public int getHeight(ImageObserver obs)
• java.awt.image.BufferedImageA blank graphic
  image surface onto which you can draw
• public BufferedImage(int w, int h, int type)
• public Graphics getGraphics()

21
Images, continued

• Code to load an image
• Toolkit tk Toolkit.getDefaultToolkit()
• Image img tk.getImage("myimage.jpg")
• MediaTracker mt new MediaTracker(this)
• mt.addImage(img, 0) // any ID will do
• try
• mt.waitForAll()
• catch (InterruptedException ie)
• This is tedious!
• suggest making a helper method to load and return
  one image
• public Image loadImage(String filename)

22
Advanced anti-aliasing

• Onscreen text and shapes can have jagged edges,
  or aliases. These can be removed by smoothing,
  or anti-aliasing, the panel.
• Graphics2D
• public void setRenderingHint(
  RenderingHints.Key key, Object value)
• Exampleg2.setRenderingHint(RenderingHints.KEY_AN
  TIALIASING, RenderingHints.VALUE_ANTIALIAS_ON)