Java: Antialiasing

Antialiased versus Aliased Graphics

When lines are drawn on the screen, vertical and horizontal lines appear perfectly straight. However, when they are on a diagonal, especially near vertical or horizontal, "jaggies" appear, giving the line a step-like appearance. This can be avoided in Java 2's Graphics2D class by requesting that edges are antialiased.

public void paintComponent(Graphics g) {
    super.paintComponent(g);
    Graphics2D g2 = (Graphics2D)g;  // See note below
    g2.setRenderingHint(RenderingHints.KEY_ANTIALIASING,
                        RenderingHints.VALUE_ANTIALIAS_ON);
    // Use g2 for all following operations
    g2.drawLine(0, 0, 100, 80);
    . . .
}

Casting to Graphics2D

The downcast in the above example from type Graphics to Graphics2D is possible because Graphics2D is a subclass of Graphics, and the parameter of the paintComponent method is already a Graphics2D object.