Java - Error in Terminal Window

Hi, I get an error in the terminal window AFTER I compile everything, and it gives me an explanation, but I don't know how to fix it. Could someone please help?

Code:

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

// -------------------------------------------------------------------------
/**
 *     
 *  @author  
 *  @version Spring, 2011 CS 1054 Intro to Java
 */
public class WatermarkImages
    extends StudentTestableGraphicsProgram
{
    //~ Instance/static variables .............................................
    public static final int APPLICATION_WIDTH = 1024;
    public static final int APPLICATION_HEIGHT = 600;
    public static final int TOLERANCE = 5;
    public static final int RGB_MAX = 255;
    
    GImage pic;
    GImage mark;
    //~ Methods ...............................................................

    // ----------------------------------------------------------
    /**
     * 
     */
    public void init()
    {
        addMouseListeners();
        String imgFile = chooseImage();
        pic = new GImage(imgFile);
        imgFile = chooseImage();
        mark = new GImage(imgFile);

        GImage marked = watermark(pic,mark);
        add(pic,0,0);
    }
    /**
     * 
     */
    public void run()
    {
        /*# add your statements here */
    }
    
    /**
     * Manipulates an image to show anything non-white and non-black in a watermark image transposed on it
     * 
     * @param img is the original image to be manipulated
     * @param water is the watermark to transpose onto img
     * @return a GImage that is the size of the smallest width and smallest height between the two images,
     *         with a watermark transposed onto the original
     */
    public GImage watermark(GImage img, GImage water)
    {
        int[][] imgArray = img.getPixelArray();
        int[][] waterArray = water.getPixelArray();
        int[][] combine;
        
        int width;
        int height;
        //find the smallest height...
        if(imgArray.length < waterArray.length)
        {
            height = imgArray.length;
        }
        else
        {
            height = waterArray.length;
        }
        //find the smallest width...
        if(imgArray[0].length < waterArray[0].length)
        {
            width = imgArray[0].length;
        }
        else
        {
            width = waterArray[0].length;
        }
        //create new 2D array the size of the smallest dimensions of both images...
        combine = new int[width][height];
        
        //traverse through 2D arrays...
        for(int i = 0; i < height; i++)
        {
            for(int j = 0; j < width; i++)
            {
                int pixel = imgArray[i][j];
                int red = GImage.getRed(pixel);
                int green = GImage.getGreen(pixel);
                int blue = GImage.getBlue(pixel);
                
                int maskPixel = waterArray[i][j];
                int maskR = GImage.getRed(maskPixel);
                int maskG = GImage.getGreen(maskPixel);
                int maskB = GImage.getBlue(maskPixel);
                
                int markedPixel;
                if( (maskR<TOLERANCE && maskG<TOLERANCE && maskB<TOLERANCE)                                   //black
                    || (maskR>(RGB_MAX-TOLERANCE) && maskG>(RGB_MAX-TOLERANCE) &&maskB>(RGB_MAX-TOLERANCE)) ) //or white
                {
                    markedPixel = pixel;    
                }
                else
                {
                    //transpose watermark shape onto original image...
                    int avg = (maskR + maskG + maskB)/3;
                    int newRed = (red+avg)/2;
                    int newGreen = (green+avg)/2;
                    int newBlue = (blue+avg)/2;
                    markedPixel = GImage.createRGBPixel(newRed,newGreen,newBlue);
                }
                combine[i][j] = markedPixel;
            }
        }
        return new GImage(combine);
    }

    /**
     * [Author: Kevin Buffardi] Saves a GImage to disk as a png file
     * @param picture A GImage picture that will be converted to png format and saved on disk
     * @param filename The name of the file to save (path optional, default to project folder.  e.g. "output.png")
     */
    public void saveImage(GImage picture, String filename)
    {
        try{
            File name = new File(filename);
            Image img = picture.getImage();
            BufferedImage buff = new BufferedImage(img.getWidth(null),img.getHeight(null),BufferedImage.TYPE_INT_RGB);
            Graphics graph = buff.getGraphics();
            graph.drawImage(img, 0, 0, null);
            graph.dispose();
            ImageIO.write(buff,"png",name);
        }
        catch(IOException e){
            System.out.println("Error when writing file: " + e.toString());
        }    
    }
    /**
     * [Author: Kevin Buffardi] Shows a file browser dialog so the user can choose a file.  
     * Only image files *should* be chosen, but this method does not prevent other types of files to be chosen.
     * @return A string representing the path and filename chosen (e.g. "C:\My Documents\image.jpg")
     */
    public String chooseImage() 
    {
        JFileChooser dialog = new JFileChooser();
        int result = dialog.showOpenDialog(this);
        if(result == JFileChooser.APPROVE_OPTION) {
            return dialog.getSelectedFile().getPath();
        }
        else
            return "";
    }
}

 

the error is:

java.lang.NegativeArraySizeException:
In file MediaTools.java on line 329.
It appears that the code is trying to create an array with a negative
size. Remember, the array must have a size that is a positive number.

This error is called a NegativeArraySizeException.

at acm.util.MediaTools.getPixelArray(MediaTools.java:329)
at acm.graphics.GImage.getPixelArray(GImage.java:336)
at WatermarkImages.watermark(WatermarkImages.java:63)
at WatermarkImages.init(WatermarkImages.java:41)
at acm.program.Program.start(Program.java:803)
at acm.program.Program.start(Program.java:1279)
java.lang.NegativeArraySizeException:
In file MediaTools.java on line 329.
It appears that the code is trying to create an array with a negative
size. Remember, the array must have a size that is a positive number.

This error is called a NegativeArraySizeException.

at acm.util.MediaTools.getPixelArray(MediaTools.java:329)
at acm.graphics.GImage.getPixelArray(GImage.java:336)
at WatermarkImages.watermark(WatermarkImages.java:62)
at WatermarkImages.init(WatermarkImages.java:41)
at acm.program.Program.start(Program.java:803)
at acm.program.Program.start(Program.java:1279)