More powerful graphics

1
More powerful graphics

• GeneralPath Class
• A child (more powerful than) the Polygon class
• Allows us to rotate and move (translate) polygons
• Graphics2D Class
• A child (more powerful than) the graphics class.
• Remember void paint (Graphics g)
• Math class
• Math.random() - Returns a double value with a
  positive sign, greater than or equal to 0.0 and
  less than 1.0.
• Math.PI -  The double value that is closer than
  any other to pi, the ratio of the circumference
  of a circle to its diameter.

2
The Star

• generate twenty randomly colored stars equally
  spaced around a circle.

3
General Path

• How would you know to use a the GeneralPath
  class.
• You wouldnt.
• Unless you were a geek, who reads Java textbooks
  as a hobby.
• Or unless you studied graphics
• GeneralPath is a way of keeping intricate points
  organized and ready for drawing
• The Class names are almost always misleading
  (FlowLayout?)

4
Graphics2D

• This Graphics2D class extends the Graphics class
  to provide more sophisticated control over
  geometry, coordinate transformations, color
  management, and text layout. This is the
  fundamental class for rendering 2-dimensional
  shapes, text and images on the Java(tm)
  platform.

5
This we know

• Extend JFrame
• Have a consructor to set up JFrame
• Have a main that instantiates the JFrame child
  class
• Have a paint method, that uses
• GeneralPath (therefore, it can use Graphics2D)
• Translate
• Rotate
• other GeneralPath and JFrame stuff

6
g.translate(200, 200)

• Moves EVERYTHING in the window 200, 200 pixels
• public void paint( Graphics g )
• // a star
• int xPoints 55, 67, 109, 73, 83, 55, 27,
  37, 1, 43
• int yPoints 0, 36, 36, 54, 96, 72, 96, 54,
  36, 36
• g.translate(200, 200)

7
Graphics2D g2d ( Graphics2D ) g

• void paint (Graphics g)
• Graphics2D g2d ( Graphics2D ) g
• Graphics2D is a child (more powerful) of graphics
• Called casting
• Gives g all the capabilities if Graphics2D

8
GeneralPath star new GeneralPath()

• int xPoints 55, 67, 109, 73, 83, 55, 27,
  37, 1, 43
• int yPoints 0, 36, 36, 54, 96, 72, 96, 54,
  36, 36
• star.moveTo( xPoints 0 , yPoints 0 )
• for ( int count 1 count count ) // prepare a line from the last
  point to... star.lineTo( xPoints count ,
  yPoints count )
• star.closePath()

9
g2d.rotate(

• g2D.rotate( someAngle )
• A single degree is 1/360 of a full turn of 2 Pi
  radians so1 (2 Pi/360) radians (pi/180)
  radians
• Pi radians 180 degrees
• Pi / 10 radians 18 degrees
• (Pi / 10 radians) 20 360 degrees
• So .. If we want to surround a circle, rotate
  1/10th Pi, 20 times

10

• // rotate around origin and draw stars in random
  colors
• for ( int count 1 count // rotate coordinate system
• g2d.rotate( Math.PI / 10 ) //
  set random drawing color (R, G, B)
  g.setColor( new Color( ( int ) (
  Math.random() 256 ), ( int ) (
  Math.random() 256 ), ( int ) (
  Math.random() 256 ) ) ) // draw filled
  star g2d.fill( star )