★ wanayoo — archive 1999 http://javaboutique.internet.com/tutorials/Java2D-Tutorial_2.html

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Java2D: An Introduction and Tutorial

by Marty Hall
Table of Contents

1. Introduction to Java2D

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);

[Move on to the next part of the article]

This article first appeared in October, 1998