// File: ImageTool.java
//
// To convert Java's Image instances to pixel arrays and back.
// Author:
//
// Modified:
// Modified:
// Modified:
//       => Simplify for greyscale, added PNG, scaling.

import java.awt.*;
import javax.swing.*;
import java.awt.event.*;
import javax.swing.event.*;
import java.awt.image.*;
import java.io.*;
import javax.imageio.*;

// A JPanel to draw the image.

class ImagePanel extends JPanel {

Image image;
boolean fitPanel = true;

public ImagePanel (Image image)
{
this.image = image;
}

public void paintComponent (Graphics g)
{
if (image == null) {
g.drawString ("No image", 50,50);
return;
}
if (fitPanel) {
g.drawImage (image, 0,0, this.getWidth(), this.getHeight(), this);
}
else {
g.drawImage (image, 0,0, this);
}
}

} // end of ImagePanel class

public class ImageTool extends JFrame {

static int locationX = 0;
static int locationY = 0;

//
/////////////////////////////////////////////////////////////
//
// The public methods. Not all are needed.

public void showImage (Image image)
{
   showImage (image, "No title");
}

public void showImage (Image image, String title)
{
// Make a frame and set parameters.
JFrame f = new JFrame ();
f.setSize (400, 300);
f.setTitle (title);
   locationX += 20;
   locationY += 20;
   f.setLocation (locationX, locationY);

// Add an instance of the image-drawing panel.
ImagePanel drawPanel = new ImagePanel (image);
Container cPane = f.getContentPane();
cPane.add (drawPanel, BorderLayout.CENTER);

// Display.
f.setDefaultCloseOperation (JFrame.EXIT_ON_CLOSE);
f.setVisible (true);
}

public void showImage (int[][][] pixels, String title)
{
showImage (pixelsToImage(pixels), title);
}

public int[][][] imageToPixels (Image image)
{
// Java's peculiar way of extracting pixels is to give them
// back as a one-dimensional array from which we will construct
// our version.
int numRows = image.getHeight (this);
int numCols = image.getWidth (this);
int[] oneDPixels = new int[numRows*numCols];

// This will place the pixels in oneDPixels[]. Each int in
// oneDPixels has 4 bytes containing the 4 pieces we need.
PixelGrabber grabber = new PixelGrabber(image, 0, 0, numCols, numRows,
oneDPixels ,0 ,numCols);
try {
grabber.grabPixels (0);
}
catch (InterruptedException e) {
System.out.println (e);
}

// Now we make our array.
int[][][] pixels = new int[numRows][numCols][4];
for(int row = 0; row < numRows; row++){
// First extract a row of int's from the right place.
int[] aRow = new int [numCols];
for(int col = 0; col < numCols; col++){
int element = row * numCols + col;
aRow[col] = oneDPixels[element];
}

// In Java, the most significant byte is the alpha value,
// followed by R, then G, then B. Thus, to extract the alpha
// value, we shift by 24 and make sure we extract only that byte.
for(int col=0; col < numCols; col++){
pixels[row][col][0] = (aRow[col] >> 24) & 0xFF; // Alpha
pixels[row][col][1] = (aRow[col] >> 16) & 0xFF; // Red
pixels[row][col][2] = (aRow[col] >> 8) & 0xFF; // Green
pixels[row][col][3] = (aRow[col]) & 0xFF;    // Blue
}
}

return pixels;
}

public int[][] imageToGreyPixels (Image image)
{
int[][][] pixels = imageToPixels (image);
return pixelsToGreyPixels (pixels);
}

Description For this problem you must use Java’s semaphore class...