Images on Applet?

[arun mahajan]

Hello,
I was trying to develop an applet on following guidance:-
1. In the aaplet I need to show about 10 images with radio button.
2. there will be a area at the top where when user selects any image it will show there.
3. I further need to have where I've to show about 5 colors (red,green etc). again with radio buttons.
4. On selecting any of these color the color of the selected image should change.
I am not able to do the point 4. can somebosy suggest any input on it to resolve the deadlock?
regards,
arun

[arun mahajan]

Hello,
Perhaps I am asking for very basic question but would be highly obliged if someone can spare his/her valuable time and show me a path.
regards,
arun

[Nathan Pruett]

What do you mean by :

On selecting any of these color the color of the selected image should change

?

Do you mean the selected color should be filtered out of the image? Do you mean that the image should have more of the selected color added to it?

[arun mahajan]

I mean by it that when a person selects one of any given color the image should become of that color. e.g.
Let us say I have a image of cow with a single color filled into it as red. now if a user selects a green color the cow should become green.
Is it possible?
Hope I am able to clear this.
regards,
Arun

[Nathan Pruett]

Here's a simple example of how to swap single colors in images. In my class "face.png" is just an image I drew of a face filled with the color red. In the code it assumes that the image starts out as red... the important part is the replaceColor() method of the inner ColorCanvas class. That grabs the pixels, swaps the colors, and rebuilds the image.

import java.awt.BorderLayout;
import java.awt.Canvas;
import java.awt.Checkbox;
import java.awt.CheckboxGroup;
import java.awt.Color;
import java.awt.Frame;
import java.awt.Graphics;
import java.awt.Image;
import java.awt.Panel;
import java.awt.Toolkit;
import java.awt.event.ItemEvent;
import java.awt.event.ItemListener;
import java.awt.event.WindowAdapter;
import java.awt.event.WindowEvent;
import java.awt.image.ImageObserver;
import java.awt.image.MemoryImageSource;
import java.awt.image.PixelGrabber;
 
public class ColorChanger extends Frame implements ItemListener {
    
    private ColorCanvas canvas;
    private CheckboxGroup colors;
    private Checkbox redCB;
    private Checkbox greenCB;
    private Checkbox blueCB;
    private Color currentColor = Color.red;
    
    public ColorChanger() {
        super( "ColorChanger" );
        Image i = Toolkit.getDefaultToolkit().getImage( "face.png" );
        canvas = new ColorCanvas( i );
        Panel buttonPanel = new Panel();
        colors = new CheckboxGroup();
        redCB = new Checkbox( "Red", colors, true );
        greenCB = new Checkbox( "Green", colors, false );
        blueCB = new Checkbox( "Blue", colors, false );
        redCB.addItemListener( this );
        greenCB.addItemListener( this );
        blueCB.addItemListener( this );
        buttonPanel.add( redCB );
        buttonPanel.add( greenCB );
        buttonPanel.add( blueCB );
        
        add( canvas, BorderLayout.CENTER );
        add( buttonPanel, BorderLayout.SOUTH );
    }
    
    public void itemStateChanged( ItemEvent evt ) {
        if ( evt.getStateChange() == ItemEvent.SELECTED ) {
            Color oldColor = currentColor;
            if ( evt.getSource() == redCB ) {
                currentColor = Color.red;
            }
            else if ( evt.getSource() == greenCB ) {
                currentColor = Color.green;
            }
            else if ( evt.getSource() == blueCB ) {
                currentColor = Color.blue;
            }
            canvas.replaceColor( oldColor, currentColor );
        }
    }
    
    public static void main(String[] args) {
        Frame f = new ColorChanger();
        f.setSize( 300, 300 );
        f.addWindowListener( new WindowAdapter() {
            public void windowClosing( WindowEvent e ) {
                System.exit( 0 );
            }
        } );
        f.setVisible( true );
    }
    
    private class ColorCanvas extends Canvas {
        
        private Image image;
        private Image buffer;
        private Graphics bg;
        
        public ColorCanvas( Image i ) {
            image = i;
        }
        
        public void update( Graphics g ) {
            paint( g );
        }
        
        public void paint( Graphics g ) {
            int width = getSize().width;
            int height = getSize().height;
            if ( buffer == null || buffer.getWidth( this ) != width || buffer.getHeight( this ) != height ) {
                buffer = createImage( width, height );
                bg = buffer.getGraphics();
            }
            bg.setColor( getBackground() );
            bg.fillRect( 0, 0, width, height );
            int imageX = ( width - image.getWidth( this ) ) / 2;
            int imageY = ( height - image.getHeight( this ) ) / 2;
            bg.drawImage( image, imageX, imageY, this );
            g.drawImage( buffer, 0, 0, this );
        }
        
        public void replaceColor( Color oldColor, Color newColor ) {
            int width = image.getWidth( this );
            int height = image.getHeight( this );
            int[] pixels = new int[ width * height ];
            PixelGrabber pg = new PixelGrabber( image, 0, 0, width, height, pixels, 0, width );
            try {
                pg.grabPixels();
            }
            catch ( InterruptedException x ) {
                x.printStackTrace();
                return;
            }
            if ( ( pg.getStatus() & ImageObserver.ABORT ) != 0 ) {
                System.err.println("image fetch aborted or errored");
                return;
            }
            for ( int i = 0; i < width * height; i++ ) {
                if ( pixels[i] == oldColor.getRGB() ) {
                    pixels[i] = newColor.getRGB();
                }
            }
            
            MemoryImageSource source = new MemoryImageSource( width, height, pixels, 0, width );
            image = createImage( source );
            repaint();
        }
    }
}