Graphics and Java 2D - Java: How to Program Early Objects - page 560

Method Description

public int getGreen()
Returns a value between 0 and 255 representing the green content.
public int getBlue()
Returns a value between 0 and 255 representing the blue content.
Graphics methods for manipulating Color s
public Color getColor()
Returns Color object representing current color for the graphics context.
public void setColor(Color c)
Sets the current color for drawing with the graphics context.

Fig. 13.4 | Color methods and color-related Graphics methods. (Part 2 of 2.)

Every color is created from a red, a green and a blue value. Together these are called
RGB values . All three RGB components can be integers in the range from 0 to 255, or all
three can be floating-point values in the range 0.0 to 1.0. The first RGB component spec-
ifies the amount of red, the second the amount of green and the third the amount of blue.
The larger the value, the greater the amount of that particular color. Java enables you to
choose from 256 256 (approximately 16.7 million) colors. Not all computers are

capable of displaying all these colors. The screen will display the closest color it can.
Two of class Color ' s constructors are shown in Fig. 13.4—one that takes three int
arguments and one that takes three float arguments, with each argument specifying the
amount of red, green and blue. The int values must be in the range 0-255 and the float
values in the range 0.0-1.0. The new Color object will have the specified amounts of red,
green and blue. Color methods getRed , getGreen and getBlue return integer values from
0 to 255 representing the amounts of red, green and blue, respectively. Graphics method
getColor returns a Color object representing the Graphics object's current drawing color.
Graphics method setColor sets the current drawing color.

× 256 ×

Drawing in Different Colors
Figures 13.5-13.6 demonstrate several methods from Fig. 13.4 by drawing filled rectangles
and String s in several different colors. When the application begins execution, class Col-
orJPanel 's paintComponent method (lines 10-37 of Fig. 13.5) is called to paint the win-
dow. Line 17 uses Graphics method setColor to set the drawing color. Method setColor
receives a Color object. The expression new Color(255, 0, 0) creates a new Color object
that represents red (red value 255 , and 0 for the green and blue values). Line 18 uses
Graphics method fillRect to draw a filled rectangle in the current color. Method fill-
Rect draws a rectangle based on its four arguments. The first two integer values represent
the upper-left x -coordinate and upper-left y -coordinate, where the Graphics object begins
drawing the rectangle. The third and fourth arguments are nonnegative integers that
represent the width and the height of the rectangle in pixels, respectively. A rectangle
drawn using method fillRect is filled by the current color of the Graphics object.