2.4 Rendering Graphics Primitives

Graphics2D provides rendering methods for Shapes, Text, and Images:

• draw--strokes a Shape's path using the Stroke and Paint objects in the Graphics2D context.
• fill--fills a Shape using the Paint in the Graphics2D context.
• drawString--renders the specified text string using the Paint in the Graphics2D context.
• drawImage--renders the specified image.

To stroke and fill a shape, you must call both the draw and fill methods.

Graphics2D also supports the draw and fill methods from previous versions of the JDK software, such as drawOval and fillRect.

2.4.1 Drawing a Shape

The outline of any Shape can be rendered with the Graphics2D.draw method. The draw methods from previous versions of the JDK software are also supported: drawLine, drawRect, drawRoundRect, drawOval, drawArc, drawPolyline, drawPolygon, draw3DRect.

When a Shape is drawn, its path is stroked with the Stroke object in the Graphics2D context. (See "Stroke Attributes" on page 19 for more information.) By setting an appropriate BasicStroke object in the Graphics2D context, you can draw lines of any width or pattern. The BasicStroke object also defines the line's endcap and join attributes.

To render shape's outline:

1. Create a BasicStroke object
2. Call Graphics2D.setStroke
3. Create the Shape.
4. Call Graphics2D.draw(shape).

In the following example, a GeneralPath object is used to define a star and a BasicStroke object is added to the Graphics2D context to define the star's line with and join attributes.

public void paint(Graphics g) {
  Graphics2D g2 = (Graphics2D) g;

  // create and set the stroke
  g2.setStroke(new BasicStroke(4.0f));

  // Create a star using a general path object
  GeneralPath p = new GeneralPath(GeneralPath.NON_ZERO);
  p.moveTo(- 100.0f, - 25.0f);
  p.lineTo(+ 100.0f, - 25.0f);
  p.lineTo(- 50.0f, + 100.0f);
  p.lineTo(+ 0.0f, - 100.0f);
  p.lineTo(+ 50.0f, + 100.0f);
  p.closePath();

  // translate origin towards center of canvas
  g2.translate(100.0f, 100.0f);

  // render the star's path
  g2.draw(p);
}

2.4.2 Filling a Shape

The Graphics2D.fill method can be used to fill any Shape. When a Shape is filled, the area within its path is rendered with the Graphics2D context's current Paint attribute--a Color, TexturePaint, or GradientPaint.

The fill methods from previous versions of the JDK software are also supported: fillRect, fill3DRect, fillRoundRect, fillOval, fillArc, fillPolygon, clearRect.

To fill a Shape:

1. Set the fill color or pattern on the graphics context using
   Graphics2D.setColor or Graphics2D.setPaint.
2. Create the Shape.
3. Call Graphics2D.fill to render the Shape.

In the following example, setColor is called to define a green fill for a Rectangle2D.

public void paint(Graphics g) {
  Graphics2D g2 = (Graphics2D) g;

  g2.setPaint(Color.green);
  Rectangle2D r2 = new Rectangle2D.Float(25,25,150,150);

  g2.fill(r2);
}

2.4.3 Rendering Text

To render a text string, you call Graphics2D.drawString, passing in the string that you want to render. For more information about rendering text and selecting fonts, see "Fonts and Text Layout" on page 45.

2.4.4 Rendering Images

To render an Image, you create the Image and call Graphics2D.drawImage. For more information about processing and rendering images, see "Imaging" on page 67.