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Java2D: An Introduction and Tutorial

This tutorial presents a quick introduction to the basics of Java2D and the use of the Graphics2D class in Java 1.2.

1.1 Overview

In Java 1.2, the paintComponent method is supplied with a Graphics2D object (a subclass of Graphics), which contains a much richer set of drawing operations. It includes pen widths, dashed lines, image and gradient color fill patterns, the use of arbitrary local fonts, a floating point coordinate system, and a number of coordinate transformation operations. However, to maintain compatibility with Swing as used in Java 1.1, the declared type of the paintComponent argument is Graphics, so you have to cast it to Graphics2D before using it.

1.2 Main New Features

• Colors and patterns: gradient fills, fill patterns from tiled images, transparency
• Local fonts
• Pen thicknesses, dashing patterns, and segment connection styles
• Coordinate transformations

1.3 General Approach

• Cast the Graphics object to a Graphics2D object
  

  public void paintComponent(Graphics g) {
    super.paintComponent(g);  // Typical Swing approach
    Graphics2D g2d = (Graphics2D)g;
    g2d.doSomeStuff(...);
    ...
  }
  

• Create a Shape object

  Rectangle2D.Double rect = ...;
  Ellipse2D.Double ellipse = ...;
  Polygon poly = ...;
  GeneralPath path = ...;
  ...
  

• Draw an outlined or solid version of the Shape

  g2d.draw(someShape);
  g2d.fill(someShape);
  

• Modify drawing 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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This tutorial was prepared by Marty Hall for work in the Research and Technology Development Center of the Johns Hopkins University Applied Physics Lab, for courses in the Johns Hopkins Part-Time MS Program in Computer Science, and for various industry seminars and courses.

© 1998 Marty Hall.Java 1.2beta4 version.

This article first appeared in November, 1998 and is reprinted with permission of the author.

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