Trail: 2D Graphics
Lesson: Overview of the Java 2D API Concepts
Java 2D Rendering
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Java 2D Rendering

The Java 2D API provides a uniform rendering model across different types of devices. At the application level, the rendering process is the same whether the target rendering device is a screen or a printer. When a component needs to be displayed, its paint or update method is automatically invoked with the appropriate Graphics context.

The Java 2D API includes the java.awt.Graphics2D class, which extends the Graphics class to provide access to the enhanced graphics and rendering features of the Java 2D API. These features include:

In addition, the Graphics2D class supports the Graphics rendering methods for particular shapes, such as drawOval and fillRect. All methods that are represented above can be divided into two groups:

  1. Methods to draw a shape
  2. Methods that affect rendering

The second group of the methods uses the state attributes that form the Graphics2D context for following purposes:

To employ Java 2D API features in the application, cast the Graphics object passed into a component’s rendering method to a Graphics2D object. For example:

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

As the following figure shows, the Graphics2D class rendering context contains several attributes.

This figure represents a stroke to outline the shape The pen attribute is applied to the outline of a shape. This stroke attribute enables you to draw lines with any point size and dashing pattern and apply end-cap and join decorations to a line.
This figure shows how to fill a shape with solid color The fill attribute is applied to a shape's interior. This paint attribute enables you to fill shapes with solid colors, gradients, and patterns.
This figure shows how to composite an existing image and a graphic primitives The compositing attribute is used when rendered objects overlap existing objects.
This figure represents shearing transform The transform attribute is applied during rendering to convert the rendered object from user space to device-space coordinates. Optional translation, rotation, scaling, or shearing transforms can also be applied through this attribute.
This figure represents how to define the clipping path by using the Shape object The clip, type restricts rendering to the area within the outline of the Shape object used to define the clipping path. Any Shape object that is used to define the clip.
This figure demonstrates a sample of glyphs

The font attribute is used to convert text strings to glyphs.

This figure represents antialiasing Rendering hints specify preferences in the trade-offs between speed and quality. For example, you can specify whether antialiasing should be used, if this feature available. See also Controlling Rendering Quality.

To learn more about transforming and compositing see the Advanced Topics in Java2D lesson.

When an attribute is set, the appropriate attribute object is passed. As the following example shows, to change the paint attribute to a blue-green gradient fill, you construct a GradientPaint object and then call the setPaint method.

gp = new GradientPaint(0f,0f,blue,0f,30f,green);
g2.setPaint(gp);

Problems with the examples? Try Compiling and Running the Examples: FAQs.
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