I completed a homework given by my instructor, but it is not doing what it's suppose to do completely.
I was able to add a message in the pixel, but if I run it, some wierd characters were added after the message
here's my work. I was only assigned to complete putSecretMessageInImage and extractSecretMessageFromImage, and instructions are given in the comments:
public class MacGuffinImageProcessor
{
/**
* This method should put the secret message
* into the pixels array. Note that the pixels
* array is an array of pixel values where the
* rgba values are all stored within singular
* integers. In other words, each int is really
* four bytes, one for each of the rgba components.
*
* Note that the message data should be placed in
* the alpha channel along the left-edge of the image,
* top to bottom.
*/
public static void putSecretMessageInImage(int[] pixels,String message)
{
int alpha = pixels[0];
alpha = alpha & 0xFFFFFF00;
int length = message.length();
alpha = alpha | length;
pixels[0] = alpha;
for (int i = 1; i < length; i++)
{
pixels[i] = message.charAt(i-1);
}
}
/**
* This method works in cooperation with the
* putSecretMessageInImage method. It must know
* how that one works in order to extract the data
* properly.
*
* This one will look at the pixel data and extract
* the text hidden inside, returning this as a String.
*/
public static String extractSecretMessageFromImage(int[] pixels)
{
String output = "";
for (int i = 1; i < pixels.length; i++)
{
output += (char)pixels[i];
}
return output;
}
}and here is the MacGuffinImageMaker class, which was given by my instructor:
import java.awt.*;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.awt.event.ItemEvent;
import java.awt.event.ItemListener;
import java.awt.image.BufferedImage;
import java.awt.image.DataBuffer;
import java.awt.image.ImageObserver;
import java.awt.image.Raster;
import java.awt.image.WritableRaster;
import java.io.File;
import java.io.IOException;
import java.net.MalformedURLException;
import java.net.URL;
import java.util.Vector;
import javax.imageio.ImageIO;
import javax.swing.*;
import javax.swing.filechooser.FileFilter;
import javax.swing.filechooser.FileNameExtensionFilter;
import javax.swing.text.html.HTMLDocument;
public class MacGuffinImageMaker extends JFrame
{
// NORTH
private JPanel northPanel;
private JLabel fileNameLabel;
private DefaultComboBoxModel dcbm;
private JComboBox fileNameComboBox;
// CENTER
private ImagePanel imagePanel;
private BufferedImage renderImage;
// SOUTH
private JPanel southPanel;
private JLabel messageLabel;
private JTextField messageTF;
private JButton setMessageButton;
// WE'LL USE THIS FOR ALL TEXT
Font font = new Font("Serif", Font.PLAIN, 20);
/**
* Default and only constructor, this lays out
* all of our GUI components.
*/
public MacGuffinImageMaker()
{
super("MacGuffin Image Maker");
setDefaultCloseOperation(EXIT_ON_CLOSE);
setExtendedState(MAXIMIZED_BOTH);
layoutGUI();
}
/**
* This sets up the entire GUI.
*/
public void layoutGUI()
{
// NORTH
northPanel = new JPanel();
fileNameLabel = new JLabel("File Name: ");
fileNameLabel.setFont(font);
fileNameComboBox = new JComboBox();
ImageItemListener iil = new ImageItemListener();
fileNameComboBox.addItemListener(iil);
northPanel.add(fileNameLabel);
northPanel.add(fileNameComboBox);
// CENTER
imagePanel = new ImagePanel();
renderImage = null;
// SOUTH
southPanel = new JPanel();
messageLabel = new JLabel("Message: ");
messageLabel.setFont(font);
messageTF = new JTextField(50);
messageTF.setFont(font);
setMessageButton = new JButton("Set Message");
southPanel.add(messageLabel);
southPanel.add(messageTF);
southPanel.add(setMessageButton);
SetMessageListener sml = new SetMessageListener();
setMessageButton.addActionListener(sml);
// ARRANGE EVERYTHING INSIDE THIS FRAME
add(northPanel, BorderLayout.NORTH);
add(imagePanel, BorderLayout.CENTER);
add(southPanel, BorderLayout.SOUTH);
// NOW THAT EVERYTHING'S IN PLACE, LET'S
// LOAD THE COMBO BOX WITH ALL THE FILE NAMES
loadComboBox();
}
/**
* This method finds all the PNG images in the
* working directory and places their file names
* in the combo box.
*/
public void loadComboBox()
{
// THIS STORES THE DATA FOR THE COMBO BOX
dcbm = new DefaultComboBoxModel();
// GET ALL THE FILES IN THIS DIRECTORY
File f = new File(".");
File[] files = f.listFiles();
Vector<String> v = new Vector<String>();
for (int i = 0; i < files.length; i++)
{
String fileName = files[i].getName();
if (fileName.endsWith(".png"))
{
dcbm.addElement(files[i].getName());
}
}
fileNameComboBox.setModel(dcbm);
// LOAD THE FIRST IMAGE
if (fileNameComboBox.getSelectedItem() != null)
{
String fileName = (String)fileNameComboBox.getSelectedItem();
loadImage(fileName);
}
}
/**
* This method checks the fileName image file. If
* it is an ARGB-type PNG it will simply load it and
* load the secret message, if any.
*
* If it is an RGB-type, it will convert it to an ARGB
* type and specify no message.
*/
public void loadImage(String fileName)
{
try
{
// READ IN THE IMAGE
File imageFile = new File(fileName);
renderImage = ImageIO.read(imageFile);
MediaTracker mt = new MediaTracker(this);
mt.addImage(renderImage, 0);
try { mt.waitForID(0); }
catch(InterruptedException ioe) {}
// IS IT AN RGB TYPE?
if (!renderImage.getColorModel().hasAlpha())
{
// LET'S CONVERT THE FILE
int w = renderImage.getWidth();
int h = renderImage.getHeight();
// MAKE A NEW BufferedImage
BufferedImage newImage = new BufferedImage(w,h,BufferedImage.TYPE_INT_ARGB);
Raster oldRaster = renderImage.getRaster();
WritableRaster newRaster = newImage.getRaster();
// AND COPY OVER ALL TEH DATA TO THE NEW ONE
for (int i = 0; i < w; i++)
{
for (int j = 0; j < h; j++)
{
int[] oldPixel = new int[3];
oldRaster.getPixel(i, j, oldPixel);
int[] newPixel = new int[4];
for(int k = 0; k < 3; k++)
newPixel[k] = oldPixel[k];
if (j == 0)
newPixel[3] = 0;
else
newPixel[3] = 255;
newRaster.setPixel(i, j, newPixel);
}
}
// NOW LET'S SAVE IT
renderImage = newImage;
saveImageToFile(fileName);
}
// IT'S AN ARGB TYPE
else
{
// SO LET'S READ IT IN AND EXTRACT
// AND THEN DISPLAY THE MESSAGE
int[] pixels = buildPixelArray();
String message = MacGuffinImageProcessor.extractSecretMessageFromImage(pixels);
messageTF.setText(message);
imagePanel.repaint();
}
}
catch(IOException ioe)
{
JOptionPane.showMessageDialog(this, "Error Reading " + fileName);
}
}
/**
* This method builds and returns an array
* of integers representing all the pixels
* in the image. Note that each int stores
* the four bytes for rgba (in that order),
* high bits to low bits.
*/
public int[] buildPixelArray()
{
Raster raster = renderImage.getRaster();
int w = raster.getWidth();
int h = raster.getHeight();
int[] pixels = new int[w * h];
int[] pixel = new int[4];
int counter = 0;
for (int i = 0; i < w; i++)
{
for (int j = 0; j < h; j++)
{
raster.getPixel(i, j, pixel);
pixels[counter] = packPixelIntoInt(pixel);
counter++;
}
}
return pixels;
}
/**
* This method packs the four integers (all 0 - 255)
* in the pixel array into a single int. This int
* is then returned.
*/
public int packPixelIntoInt(int[] pixel)
{
int pixelInt = 0;
pixelInt = pixel[0] << 24;
pixelInt = pixelInt | (pixel[1] << 16);
pixelInt = pixelInt | (pixel[2] << 8);
pixelInt = pixelInt | pixel[3];
return pixelInt;
}
/**
* This method provides the architecture for adding
* the secret message. Note that the implementation
* is done inside the MacGuffinImageProcessor class.
*/
public void addSecretMessageToImage(String newFileName,
String message)
{
// IF IT'S A NEW FILE NAME, WE NEED TO
// ADD IT TO THE COMBO BOX
if (dcbm.getIndexOf(newFileName) == -1)
{
// IS IT THE FIRST ELEMENT?
if (dcbm.getSize() == 0)
dcbm.addElement(newFileName);
// DOES IT GO AT THE END?
else
{
String lastFileName = (String)dcbm.getElementAt(dcbm.getSize()-1);
if (newFileName.compareTo(lastFileName) > 0)
dcbm.addElement(newFileName);
// IT MUST GO SOMEWHERE ELSE
else
{
boolean locationFound = false;
for (int i = 0; (i < dcbm.getSize()) && !locationFound; i++)
{
String testFileName = (String)dcbm.getElementAt(i);
if (newFileName.compareTo(testFileName) < 0)
{
dcbm.insertElementAt(newFileName, i);
locationFound = true;
}
}
}
}
}
int[] pixels = buildPixelArray();
MacGuffinImageProcessor.putSecretMessageInImage(pixels, message);
updatePixels(pixels);
saveImageToFile(newFileName);
fileNameComboBox.setSelectedItem(newFileName);
}
/**
* This method would be called after a secret
* message has been put into a pixels array, which
* is the method argument. This method will then
* load this data into the image.
*/
public void updatePixels(int[] pixels)
{
WritableRaster wr = renderImage.getRaster();
int length = pixels[0] & 0x000000ff;
for (int i = 0; i <= length; i++)
{
int[] pixel = new int[4];
pixel[0] = (pixels[i] >> 25) & 0x000000ff;
pixel[1] = (pixels[i] & 0x00ff0000)>>16;
pixel[2] = (pixels[i] & 0x0000ff00)>>8;
pixel[3] = (pixels[i] & 0x000000ff);
wr.setPixel(0, i, pixel);
}
}
/**
* This method saves the image, with the secret
* message, to its file.
*/
public void saveImageToFile(String fileName)
{
try
{
File f = new File(fileName);
ImageIO.write(renderImage, "png", f);
}
catch(IOException ioe)
{
ioe.printStackTrace();
}
}
/**
* This helper class responds to the user selecting
* an image from the combo box. It does so by loading
* the selected image, rendering it, and loading and
* displaying any secret message found inside.
*/
private class ImageItemListener implements ItemListener
{
public void itemStateChanged(ItemEvent ie)
{
if (ie.getStateChange() == ItemEvent.SELECTED)
{
String fileName = (String)ie.getItem();
loadImage(fileName);
}
}
}
/**
* This helper class provides the response for when
* the user clicks on the Set Message button. At that
* time, we want to take the text in the text field and
* embed it inside the image.
*/
private class SetMessageListener implements ActionListener
{
public void actionPerformed(ActionEvent ae)
{
// THIS IS THE IMAGE WE'RE USING
BufferedImage img = MacGuffinImageMaker.this.renderImage;
if (img != null)
{
// FIRST ASK THE USER WHAT TO NAME THE IMAGE
String fileName = JOptionPane.showInputDialog(
MacGuffinImageMaker.this,
"What would you like to name your "
+ " image with the secret message?",
MacGuffinImageMaker.this.fileNameComboBox.getSelectedItem());
if (fileName != null)
{
int w = img.getWidth(null);
int h = img.getHeight(null);
String secretMessage = MacGuffinImageMaker.this.messageTF.getText();
if (secretMessage.length() > (h-1))
JOptionPane.showMessageDialog(MacGuffinImageMaker.this, "For this image, your message is too long. It many not have more than " + w + " characters", "Message too long", JOptionPane.ERROR_MESSAGE);
else
MacGuffinImageMaker.this.addSecretMessageToImage(fileName, secretMessage);
}
}
}
}
/**
* This helper class performs all the image
* rendering inside our application.
*/
private class ImagePanel extends JPanel
{
public void paintComponent(Graphics g)
{
super.paintComponent(g);
Image img = MacGuffinImageMaker.this.renderImage;
if (img != null)
{
int w = getWidth();
int h = getHeight();
if (w > 0)
{
int imgW = img.getWidth(null);
int imgH = img.getHeight(null);
int x = (w/2) - (imgW/2);
int y = (h/2) - (imgH/2);
g.drawImage(img, x, y, null);
}
}
}
}
/**
* This is where our program starts. We make a new
* window (our MacGuffinImageMaker object), and start
* it up. Once started, the program is in event-
* handling mode, waiting for the user to do something.
*/
public static void main(String[] args)
{
MacGuffinImageMaker frame = new MacGuffinImageMaker();
frame.setVisible(true);
}
}Could anyone point out what I did wrong here? I'm assuming that my putSecretMessageInImage() works but the problem is in the extractSecretMessageInImage()...I could be wrong both ways
