Gradient Filter problem

[alanchan]

I had tried to build a gradient filter for image processing,which when the filter is applied,a dark gardient will appear at the bottom right of the image, and gradually fade out at the top left corner(see the attachment pls).
But after I run the filter, I found that nothing had applied onto the photos,
even I changed the color of the gradient. Can anyone figure out why this happen? thx~~

the code is like this:

import java.awt.image.BufferedImage;
import java.io.File;
import javax.imageio.ImageIO;
import javax.swing.JOptionPane;
import java.awt.Color;
import java.awt.GradientPaint;
import java.awt.Graphics2D;

public class gradientFilter{
final private static String DEFAULT_OUTFILE_NAME = "new";
static int IMG_WIDTH, IMG_HEIGHT;
static BufferedImage initialImg, processImg, newImg;
private String openFile = null;



public gradientFilter(String name){
openFile=name;
}

public BufferedImage imGradient (BufferedImage imIn,int type, int h, int w){
BufferedImage imGradient=new BufferedImage(w,h, type);

GradientPaint gp=new GradientPaint((float)0,(float)0,Color.WHITE,(float )w,(float)h,Color.PINK,true);
Graphics2D g =imGradient.createGraphics();
g.drawImage(imIn,0,0,w,h,null);
g.setPaint(gp);
g.dispose();
return imGradient;
}

private void setGradient() throws java.io.IOException{
initialImg = ImageIO.read(new File(openFile));
int type = initialImg.getType() == 0? BufferedImage.TYPE_INT_ARGB : initialImg.getType();
IMG_WIDTH = initialImg.getWidth();
IMG_HEIGHT = initialImg.getHeight();
newImg = imGradient(initialImg, type, IMG_HEIGHT, IMG_WIDTH);

}


public static void main(String[] args){
try{
String name = JOptionPane.showInputDialog("Please enter the file you wish to load (filename.type):", args[0]);
if (name.length()<=0)
name = args[0];

String newName = JOptionPane.showInputDialog("Save as:", DEFAULT_OUTFILE_NAME);
if (newName.length()<=0)
newName = DEFAULT_OUTFILE_NAME;

newName = newName+".png";

gradientFilter opcg = new gradientFilter(name);
opcg.setGradient();


ImageIO.write(newImg, "png", new File(newName));
}
catch(java.io.IOException e){
System.out.println("ERROR: cannot save image");
}
catch(NullPointerException e){
}
}
}