Using Color, Fonts, and Graphics - Java 6 - page 363

Java2D offers a wide range of attributes for designating color, including line width, fill
patterns, transparency, and many other features.

Fill Patterns
Fill patterns control how a drawn object will be filled in. With Java2D, you can use a
solid color, gradient fill, texture, or pattern of your own devising.

A fill pattern is defined by using the setPaint( Paint ) method of Graphics2D with a
Paint object as its only argument. Any class that can be a fill pattern, including
GradientPaint , TexturePaint , and Color , can implement the Paint interface. Using a
Color object with setPaint() is the same thing as using a solid color as the pattern.

A gradient fill is a gradual shift from one color at one coordinate point to another color
at a different coordinate point. The shift can occur once between the points—which is
called an acyclic gradient —or it can happen repeatedly, which is a cyclic gradient .

Figure 13.3 shows examples of acyclic and cyclic gradients between white and a darker
color. The arrows indicate the points that the colors shift between.

Acyclic Cyclic

FIGURE 13.3
Acyclic and cyclic
gradient shifts.

The coordinate points in a gradient do not refer directly to points on the Graphics2D
object being drawn onto. Instead, they refer to user space and can even be outside the
object being filled with a gradient.

Figure 13.4 illustrates this. Both rectangles are filled using the same GradientPaint
object as a guide. One way to think of a gradient pattern is as a piece of fabric that has
been spread over a flat surface. The shapes being filled with a gradient are the patterns
cut from the fabric, and more than one pattern can be cut from the same piece of cloth.

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A call to the GradientPaint constructor method takes the following format:

GradientPaint gp = new GradientPaint(
x1, y1, color1, x2, y2, color2);

The point x1 , y1 is where the color represented by color1 begins, and x2 , y2 is where
the shift ends at color2 .