Changing RGB values of a color over time

Question

I want to create a background color that transitions smoothly between colors by changing its RGB values incrementally. I am using the setBackground(Color) to change the background.

Would this be possible in Java?

Answer 1

Here is some old code that changes the background Color when a component gains focus.

import java.awt.*;
import java.awt.event.*;
import java.util.Hashtable;
import java.util.ArrayList;
import javax.swing.*;

public class Fader
{
    //  background color when component has focus
    private Color fadeColor;

    //  steps to fade from original background to fade background
    private int steps;

    //  apply transition colors at this time interval
    private int interval;

    //  store transition colors from orginal background to fade background
    private Hashtable backgroundColors = new Hashtable();

    /*
     *  Fade from a background color to the specified color using
     *  the default of 10 steps at a 50 millisecond interval.
     *
     *  @param fadeColor the temporary background color
     */
    public Fader(Color fadeColor)
    {
        this(fadeColor, 10, 50);
    }

    /*
     *  Fade from a background color to the specified color in the
     *  specified number of steps at the default 5 millisecond interval.
     *
     *  @param fadeColor the temporary background color
     *  @param steps     the number of steps to fade in the color
     */
    public Fader(Color fadeColor, int steps)
    {
        this(fadeColor, steps, 50);
    }

    /*
     *  Fade from a background color to the specified color in the
     *  specified number of steps at the specified time interval.
     *
     *  @param fadeColor the temporary background color
     *  @param steps     the number of steps to fade in the color
     *  @param intevral  the interval to apply color fading
     */
    public Fader(Color fadeColor, int steps, int interval)
    {
        this.fadeColor = fadeColor;
        this.steps = steps;
        this.interval = interval;
    }

    /*
     *  Add a component to this fader.
     *
     *  The fade color will be applied when the component gains focus.
     *  The background color will be restored when the component loses focus.
     *
     *  @param component apply fading to this component
    */
    public Fader add(JComponent component)
    {
        //  Get colors to be used for fading

        ArrayList colors = getColors( component.getBackground() );

        //  FaderTimer will apply colors to the component

        new FaderTimer( colors, component, interval );

        return this;
    }

    /*
    **  Get the colors used to fade this background
    */
    private ArrayList getColors(Color background)
    {
        //  Check if the color ArrayList already exists

        Object o = backgroundColors.get( background );

        if (o != null)
        {
            return (ArrayList)o;
        }

        //  Doesn't exist, create fader colors for this background

        ArrayList colors = new ArrayList( steps + 1 );
        colors.add( background );

        int rDelta = ( background.getRed() - fadeColor.getRed() ) / steps;
        int gDelta = ( background.getGreen() - fadeColor.getGreen() ) / steps;
        int bDelta = ( background.getBlue() - fadeColor.getBlue() ) / steps;

        for (int i = 1; i < steps; i++)
        {
            int rValue = background.getRed() - (i * rDelta);
            int gValue = background.getGreen() - (i * gDelta);
            int bValue = background.getBlue() - (i * bDelta);

            colors.add( new Color(rValue, gValue, bValue) );
        }

        colors.add( fadeColor );
        backgroundColors.put(background, colors);

        return colors;
    }

    class FaderTimer implements FocusListener, ActionListener
    {
        private ArrayList colors;
        private JComponent component;
        private Timer timer;
        private int alpha;
        private int increment;

        FaderTimer(ArrayList colors, JComponent component, int interval)
        {
            this.colors = colors;
            this.component = component;
            component.addFocusListener( this );
            timer = new Timer(interval, this);
        }

        public void focusGained(FocusEvent e)
        {
            alpha = 0;
            increment = 1;
            timer.start();
        }

        public void focusLost(FocusEvent e)
        {
            alpha = steps;
            increment = -1;
            timer.start();
        }

        public void actionPerformed(ActionEvent e)
        {
            alpha += increment;

            component.setBackground( (Color)colors.get(alpha) );

            if (alpha == steps || alpha == 0)
                timer.stop();
        }
    }

    public static void main(String[] args)
    {
        // Create test components

        JComponent textField1 = new JTextField(10);
        textField1.setBackground( Color.YELLOW );
        JComponent textField3 = new JTextField(10);
        JComponent textField4 = new JTextField(10);
        JComponent button = new JButton("Start");
        JComponent checkBox = new JCheckBox("Check Box");

        JFrame frame = new JFrame("Fading Background");
        frame.setDefaultCloseOperation( JFrame.EXIT_ON_CLOSE );
        frame.getContentPane().add(textField1, BorderLayout.NORTH );
        frame.getContentPane().add(button, BorderLayout.SOUTH );
        frame.getContentPane().add(textField3, BorderLayout.WEST );
        frame.getContentPane().add(textField4, BorderLayout.EAST );
        frame.getContentPane().add(checkBox);

        //  Gradual Fading (using defaults)

//      Fader fader = new Fader( new Color(155, 255, 155) );
        Fader fader = new Fader( new Color(155, 255, 155), 10, 50 );
        fader.add( textField1 );
        fader.add( textField3 );
        fader.add( checkBox );

        //  Instant Fading

        fader = new Fader( new Color(255, 155, 155), 1, 1 );
        fader.add( textField4 );
        fader.add( button );

        frame.pack();
        frame.setVisible( true );
    }
}

Answer 2

This sounds like a job for java.swing.Timer. You can fire it off periodically to change the background color. Here's a tutorial on how to use it. Try this out, it will eventually crash, but it's a good proof of concept:

package com.sandbox;

import javax.swing.*;
import java.awt.*;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;

public class Sandbox implements ActionListener{

    private static Color startColor;
    private JPanel contentPane;

    public static void main(String[] args) {
        new Sandbox().run();
    }

    private void run() {
        JFrame frame = new JFrame();
        frame.setDefaultCloseOperation(WindowConstants.EXIT_ON_CLOSE);

        contentPane = new JPanel();
        startColor = new Color(200, 100, 100);
        contentPane.setBackground(startColor);

        frame.setContentPane(contentPane);
        frame.setVisible(true);

        new Timer(1000, this).start();
    }

    @Override
    public void actionPerformed(ActionEvent e) {
        startColor = new Color(startColor.getRed() - 10, startColor.getGreen(), startColor.getBlue() + 10);
        contentPane.setBackground(startColor);
    }
}