The Java 2D™ API is powerful and complex. However, the vast majority of uses for the Java 2D API utilize a small subset of its capabilities encapsulated in the java.awt.Graphics class. This lesson covers the most common needs of applications developers. Less common needs are described later in the Advanced topics in the Java 2D API lesson.

Most methods of the Graphics class can by divided into two basic groups:

• Draw and fill methods, enabling you to render basic shapes, text, and images
• Attributes setting methods, which affect how that drawing and filling appears

Methods such as setFont and setColor define how draw and fill methods render.

This figure illustrates how these methods relate to graphic objects:

Drawing methods include:

• drawString – For drawing text

   g.drawString("Hello", 10, 10);

• drawImage – For drawing images

   g.drawImage(img, 
                    0, 0, width, height,
                    0, 0, imageWidth, imageHeight,
                    null);                    

• drawLine, drawArc, drawRect, drawOval, drawPolygon – For drawing geometric shapes

g2.draw(new Line2D.Double(0, 0, 30, 40));

Depending on your current need, you can choose one of the several methods in the Graphics class based on the following criteria:

• Whether you want to render the image at the specified location and its original size or scaling it to fit inside the given rectangle
• Whether you prefer to fill the transparent areas of the image with color or keep them transparent

Fill methods apply to geometric shapes and include fillArc, fillRect, fillOval, fillPolygon.

Whether you draw a line of text or an image, remember that in 2D graphics, every point is determined by its x and y coordinates. All of the draw and fill methods need this information, which determines where the text or image should be rendered.

For example, to draw a line, an application calls the following:

java.awt.Graphics.drawLine(int x1, int y1, int x2, int y2)

In this code (x1, y1) is the start point of the line, and (x2, y2) is the end point of the line.

So the code to draw a horizontal line is as follows:

Graphics.drawLine(20, 100, 120, 100);

This code example generates a simple image label:

ImageLabel.java contains the complete code for this example.