The Java Boutique: Articles : Java 2D

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Java2D: An Introduction and Tutorial

Contents
Introduction
Drawing Shapes
Paint Styles
Transparency
Using Local Fonts
Stroke Styles
Coordinate Transformations
Conclusions

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);

Next ->

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.

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

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