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Java2D: An Introduction and Tutorial

8. Conclusions

8.1 Requesting More Accurate Drawing: Rendering Hints

Since Java2D already does a lot of calculations compared to the old AWT, there are several optional features that the designers chose to disable by default in order to improve performance. Turning them on results in crisper drawing, especially for rotated text. For example, the JTable on envisioning transformations resulted in excessively jagged text using the default settings.

The most important two settings are to turn on antialiasing (smooth jagged lines by blending colors) and to simply request the highest-quality rendering. This approach is illustrated below:

RenderingHints renderHints =
  new RenderingHints(RenderingHints.KEY_ANTIALIASING,
    RenderingHints.VALUE_ANTIALIAS_ON);
  renderHints.put(RenderingHints.KEY_RENDERING,
    RenderingHints.VALUE_RENDER_QUALITY);

...

public void paintComponent(Graphics g) {
  super.paintComponent(g);
  Graphics2D g2d = (Graphics2D)g;
  g2d.setRenderingHints(renderHints);
  ...
}

8.2 Summary of Using Java2D

• Cast Graphics to Graphics2D wherever you have a Graphics object
• Create Shape objects, then call Graphics2D's draw and fill methods with shapes as args.
• Use setPaint to specify a solid color (Color), a gradient fill (GradientPaint), or tiled image (TexturePaint). TexturePaint requires a BufferedImage, which you can create from an image file by creating empty BufferedImage then drawing image into it.
• Use AlphaComposite for transparency. Create one via AlphaComposite.getInstance with a type of AlphaComposite.SRC_OVER.
• Local fonts: before using them you must call GraphicsEnvironment.getLocalGraphicsEnvironment().getAllFonts() or GraphicsEnvironment.getLocalGraphicsEnvironment().getAvailableFontFamilyNames(). Then supply name to Font constructor and specify font via setFont, as in Java 1.1.
• BasicStroke lets you set pen thickness, dashing pattern, and line cap/join styles. Supply it to Graphics2D via setStroke.
• Coordinate transforms let you move the coordinate system (e.g. the piece of paper you're drawing on) rather than changing what you draw. Do simple transforms via the translate, rotate, scale, and shear methods of Graphics2D. Do more complex transforms by supplying transformation matrix to AffineTransform constructor, then calling Graphics2D's setTransform method.
• Improve drawing quality or enable antialiasing through use of rendering hints.

8.3 Other Capabilities of Java2D

• High-quality printing (see this printing tutorial)
• Improved XOR mode
• Custom color mixing (implement Composite and CompositeContext interfaces)
• Bounds/hit testing (see contains and intersects methods of Shape)
• Fancy text operations
  • Create new fonts by transforming old ones (use Font.deriveFont)
  • Draw multi-font or multi-color strings (use the draw method of TextLayout)
  • Draw outlines of fonts, or fill fonts with images or gradient colors (use the getOutline method of TextLayout)
• Low-level image processing and color model manipulation

8.4 Learning More About Java2D

• Java2D home page
• Java2D FAQ
• Java2D guide overview
• Java2D API Guide
• Tutorial on text in Java2D
• Tutorial on printing in Java2D

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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