• Purpose:
  • Determine how to present graphics primitives on a visual output device
• In Java:
  • The rendering engine is a Graphics2D object

The (Linear) Color Cube

• The RGB Model:
  • Begin with black then add red, green, and or blue
  • An additive model
  • Often used for displays/monitors
• The CMYK Model:
  • Begin with white then remove cyan, magenta, and/or yellow
  • A subtractive model
  • Often used for printing

• Coordinates:
  • Quantities (linear and/or angular) that designate the position of a point in relation to a given reference frame
• In Java:
  • 

• Geometric Shapes (see the Shape interface):
  • draw(Shape s)
  • fill(Shape s)
• Strings/Text:
  • drawString(String s, float x, float y)
• Images:
  • drawImage(Image i, int x, int y, null)

• 0-Dimensional:
  • Points (Point2D )
• 1-Dimensional:
  • Lines (Line2D )
  • Curves (CubicCurve2D and QuadCurve2D )
• 2-Dimensional:
  • Rectangles(Rectangle2D )
  • Polygons (GeneralPath )
  • Ellipses (Ellipse2D )

• Stroke:
  • The line "style" (see the Stroke interface)
  • Set using the setStroke method in Graphics2D
• Color:
  • The line color (see the Color class)
  • Set using the setColor method in Graphics2D

Joins and Caps

• Paint:
  • The fill "style" and color (see the Paint interface)
  • Set using the setPaint method in Graphics2D
• Types:
  • Color
  • GradientPaint
  • TexturePaint

• Font:
  • The "glyphs" used for each character
  • Set using the setFont method in Graphics2D
• Properties:
  • Name
  • Size (in points)
  • Style (plain, italic, bold)

Line Metrics

The x and y passed to drawString(String s, float x, float y) are the left end of the baseline.

• FontRenderContext
  • Keeps information about fonts
• LineMetrics
  • Keeps information about font and line heights

• BufferedImage Class:
  • Extends the abstract Image class
  • Objects can be read from a file using the static read() method in the ImageIO class
• The drawImage(Image i, int x, int y, null) Method:
  • x and y determine where the the upper-left corner of the Image will be rendered

• Motivation:
  • You need a GUI component to render in
  • You can extend any GUI component, you just need to override the public void paint(Graphics g) method
• A Good Class to Extend:
  • JComponent which does very little in its paint() method

javaexamples/multimedia/Example.java

import java.awt.*;
import java.awt.geom.*;
import javax.swing.*;

/**
 * A simple example of graphics
 *
 * @author  Prof. David Bernstein, James Madison University
 * @version 1.0
 */
public class Example extends JComponent
{
    public static final float[] DASHED_PATTERN = {10.0f, 10.0f};
    public static final float[] DOTTED_PATTERN = { 2.0f,  2.0f};


    /**
     * Render this JComponent
     *
     * @param g   The rendering engine to use
     */
    public void paint(Graphics g)
    {
       Font                  serifFont;
       GradientPaint         gradient;
       Graphics2D            g2;        
       Line2D.Float          line;
       Path2D.Float          path;
       Rectangle2D.Float     rectangle;
       Stroke                dashed, dotted, solid;

       g2 = (Graphics2D)g;


       // Create some Stroke objects
       dashed = new BasicStroke(2.0f,
                                BasicStroke.CAP_BUTT, 
                                BasicStroke.JOIN_MITER,
                                10.0f,
                                DASHED_PATTERN,
                                0.0f);

       dotted = new BasicStroke(2.0f,
                                BasicStroke.CAP_BUTT, 
                                BasicStroke.JOIN_MITER,
                                10.0f,
                                DOTTED_PATTERN,
                                0.0f);

       solid  = new BasicStroke(2.0f, 
                                BasicStroke.CAP_BUTT,
                                BasicStroke.JOIN_MITER);

       // Create a Font object
       serifFont = new Font(Font.SERIF, Font.PLAIN, 20);



       // Create and render some lines
       g2.setColor(Color.red);

       line = new Line2D.Float(0f,0f,100f,100f);
       g2.draw(line);

       line = new Line2D.Float(100f,100f,200f,200f);
       g2.setStroke(dashed);
       g2.draw(line);

       line = new Line2D.Float(200f,200f,300f,300f);
       g2.setStroke(dotted);
       g2.draw(line);

        
       // Render some text
       g2.setColor(Color.blue);

       g2.setFont(serifFont);
       g2.drawString("Hello World",40.0f,100.0f);


       // Create a Paint object
       gradient = new GradientPaint(300.0f,300.0f,Color.green,
                                    500.0f,300.0f,Color.yellow);

       // Create and render a rectangle
       rectangle = new Rectangle2D.Float(300f,300f,200f,100f);
       g2.setPaint(gradient);
       g2.fill(rectangle);
       g2.setStroke(solid);
       g2.setColor(Color.black);
       g2.draw(rectangle);

       // Create and render a Path2D
       path = new Path2D.Float();
       path.moveTo(100.0f,300.0f);
       path.lineTo(200.0f,400.0f);
       path.lineTo(100.0f,350.0f);
       path.lineTo(  0.0f,400.0f);
       path.lineTo(100.0f,300.0f);

       g2.draw(path);
    }
}
        

javaexamples/multimedia/ExampleDriver.java

import java.awt.*;
import javax.swing.*;


/**
 * A simple example of graphics
 *
 * @author  Prof. David Bernstein, James Madison University
 * @version 1.0
 */
public class ExampleDriver
{
    /**
     * The entry point
     *
     * @param args   The command line arguments
     */
    public static void main(String[] args)
    {
       Container      contentPane;
       Example        example;
       JFrame         window;
        

       window      = new JFrame("Graphics Example");
       contentPane = window.getContentPane();
       contentPane.setLayout(null);
       example = new Example();
       example.setBounds(0,0,500,500);
       window.add(example);
       window.setSize(600,600);
       window.setVisible(true);
    }
}