Java 2D Graphics

2.1. Graphics2D

Rendering is the process of taking a collection of shapes, text, and images and figuring out what colors the pixels should be on a screen or printer. Shapes, text, and images are called graphics primitives ; screens and printers are called output devices. If I wanted to be pompous, I'd tell you that rendering is the process of displaying graphics primitives on output devices. A rendering engine performs this work; in the 2D API, the Graphics2D class is the rendering engine. Figure 2.1 shows this process at a high level. The 2D rendering engine takes care of the details of underlying devices and can accurately reproduce the geometry and color of a drawing, regardless of the device that displays it.

Figure 2.1. Rendering, the short story

Apart from being a rendering engine, an instance of Graphics2D also represents a drawing surface, which is simply some collection of pixels, each of which holds a color. It might be the inside of a window or a page in a printer, or even an offscreen image. Each time you draw something new, the new element is added to the existing drawing represented by the Graphics2D.