Grayscale value of a pixel in an image

Question

Hi all,
I have an image . I want to read the image and find out its grayscale value of each pixel.
I have carried out several methods and used variety of classes to get the value of each pixel but all my effort went in vain.
It would be great if someone could write it for me from scratch.
Regards.

Answer 1

import java.awt.*;
import java.awt.event.*;
import java.awt.image.BufferedImage;
import java.io.*;
import javax.imageio.ImageIO;
import javax.swing.*;
public class GrayReader extends JPanel
    BufferedImage image;
    BufferedImage grayImage;
    JLabel label;
    JLabel red;
    JLabel green;
    JLabel blue;
    JLabel gray;
    public void showPixel(Point p)
        int rgb = image.getRGB(p.x, p.y);
        int r = (rgb >> 16) & 0xff;
        int g = (rgb >>  8) & 0xff;
        int b = (rgb >>  0) & 0xff;
        int grgb = grayImage.getRGB(p.x, p.y);
        int gVal = grgb & 0xff;
        red.setText(String.valueOf(r));
        green.setText(String.valueOf(g));
        blue.setText(String.valueOf(b));
        gray.setText(String.valueOf(gVal));
    private JPanel getImagePanel(MouseMotionListener l)
        label = new JLabel();
        label.addMouseMotionListener(l);
        JPanel panel = new JPanel(new GridBagLayout());
        GridBagConstraints gbc = new GridBagConstraints();
        gbc.insets = new Insets(10,10,10,10);
        panel.add(label, gbc);
        return panel;
    private JPanel getUIPanel(final Frame f)
        // row 1
        red = new JLabel(" ");
        green = new JLabel(" ");
        blue = new JLabel(" ");
        gray = new JLabel(" ");
        Dimension d = red.getPreferredSize();
        d.width = 45;
        GridBagLayout gridbag = new GridBagLayout();
        GridBagConstraints gbc = new GridBagConstraints();
        gbc.insets = new Insets(2,2,2,2);
        gbc.weightx = 1.0;
        JPanel row1 = new JPanel(gridbag);
        addComponents(new JLabel("r:"),    red,   row1, gbc, d);
        addComponents(new JLabel("g:"),    green, row1, gbc, d);
        addComponents(new JLabel("b:"),    blue,  row1, gbc, d);
        addComponents(new JLabel("gray:"), gray,  row1, gbc, d);
        // row 2
        JButton open = new JButton("open");
        open.addActionListener(new ActionListener()
            JFileChooser fileChooser = new JFileChooser("images");
            public void actionPerformed(ActionEvent e)
                if(fileChooser.showOpenDialog(f) == JFileChooser.APPROVE_OPTION)
                    File file = fileChooser.getSelectedFile();
                    try
                        image = ImageIO.read(file);
                    catch(IOException ioe)
                        System.out.printf("read error: " + ioe.getMessage());
                    // make a gray image to read pixels from
                    grayImage = new BufferedImage(image.getWidth(),
                                                  image.getHeight(),
                                                  BufferedImage.TYPE_BYTE_GRAY);
                    Graphics2D g2 = grayImage.createGraphics();
                    g2.drawRenderedImage(image, null);
                    g2.dispose();
                    // update gui
                    label.setIcon(new ImageIcon(image));
                    revalidate();
                    repaint();
        JPanel row2 = new JPanel();
        row2.add(open);
        JPanel panel = new JPanel(gridbag);
        gbc.insets = new Insets(0,0,0,0);
        gbc.gridwidth = GridBagConstraints.REMAINDER;
        gbc.fill = GridBagConstraints.HORIZONTAL;
        panel.add(row1, gbc);
        panel.add(row2, gbc);
        return panel;
    private void addComponents(Component c1, Component c2, Container c,
                               GridBagConstraints gbc, Dimension d)
        gbc.anchor = GridBagConstraints.EAST;
        c.add(c1, gbc);
        c2.setPreferredSize(d);
        gbc.anchor = GridBagConstraints.WEST;
        c.add(c2, gbc);
    public static void main(String[] args)
        GrayReader grayReader = new GrayReader();
        PixelRanger ranger = new PixelRanger(grayReader);
        JPanel imagePanel = grayReader.getImagePanel(ranger);
        JFrame f = new JFrame();
        f.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        f.getContentPane().add(new JScrollPane(imagePanel));
        f.getContentPane().add(grayReader.getUIPanel(f), "Last");
        f.setSize(400,400);
        f.setLocation(200,200);
        f.setVisible(true);
class PixelRanger extends MouseMotionAdapter
    GrayReader grayReader;
    public PixelRanger(GrayReader gr)
        grayReader = gr;
    public void mouseMoved(MouseEvent e)
        grayReader.showPixel(e.getPoint());
}