ColorGradient.java Source code

Introduction

Here is the source code for ColorGradient.java

Source

/*
* Copyright (c) 2000 David Flanagan.  All rights reserved.
* This code is from the book Java Examples in a Nutshell, 2nd Edition.
* It is provided AS-IS, WITHOUT ANY WARRANTY either expressed or implied.
* You may study, use, and modify it for any non-commercial purpose.
* You may distribute it non-commercially as long as you retain this notice.
* For a commercial use license, or to purchase the book (recommended),
* visit http://www.davidflanagan.com/javaexamples2.
*/

import java.applet.Applet;
import java.awt.Color;
import java.awt.Component;
import java.awt.Font;
import java.awt.Graphics;
import java.awt.Rectangle;
import java.awt.event.WindowAdapter;
import java.awt.event.WindowEvent;
import javax.swing.JFrame;

/** An applet that demonstrates the Color class */
public class ColorGradient extends Applet {
    Color startColor, endColor; // Start and end color of the gradient

    Font bigFont; // A font we'll use

    /**
     * Get the gradient start and end colors as applet parameter values, and
     * parse them using Color.decode(). If they are malformed, use white.
     */
    public void init() {
        try {
            startColor = Color.decode(getParameter("startColor"));
            endColor = Color.decode(getParameter("endColor"));
        } catch (Exception e) {
            startColor = Color.yellow;
            endColor = Color.red;
        }
        bigFont = new Font("Helvetica", Font.BOLD, 72);
    }

    /** Draw the applet. The interesting code is in fillGradient() below */
    public void paint(Graphics g) {
        fillGradient(this, g, startColor, endColor); // display the gradient
        g.setFont(bigFont); // set a font
        g.setColor(new Color(100, 100, 200)); // light blue
        g.drawString("Colors!", 100, 100); // draw something interesting
    }

    /**
     * Draw a color gradient from the top of the specified component to the
     * bottom. Start with the start color and change smoothly to the end
     */
    public void fillGradient(Component c, Graphics g, Color start, Color end) {
        Rectangle bounds = this.getBounds(); // How big is the component?
        // Get the red, green, and blue components of the start and end
        // colors as floats between 0.0 and 1.0. Note that the Color class
        // also works with int values between 0 and 255
        float r1 = start.getRed() / 255.0f;
        float g1 = start.getGreen() / 255.0f;
        float b1 = start.getBlue() / 255.0f;
        float r2 = end.getRed() / 255.0f;
        float g2 = end.getGreen() / 255.0f;
        float b2 = end.getBlue() / 255.0f;
        // Figure out how much each component should change at each y value
        float dr = (r2 - r1) / bounds.height;
        float dg = (g2 - g1) / bounds.height;
        float db = (b2 - b1) / bounds.height;

        // Now loop once for each row of pixels in the component
        for (int y = 0; y < bounds.height; y++) {
            g.setColor(new Color(r1, g1, b1)); // Set the color of the row
            g.drawLine(0, y, bounds.width - 1, y); // Draw the row
            r1 += dr;
            g1 += dg;
            b1 += db; // Increment color components
        }
    }

    public static void main(String[] a) {
        JFrame f = new JFrame();
        f.addWindowListener(new WindowAdapter() {
            public void windowClosing(WindowEvent e) {
                System.exit(0);
            }
        });
        ColorGradient g = new ColorGradient();
        g.init();

        f.setContentPane(g);
        f.setSize(600, 200);
        f.setVisible(true);
    }

}