Re: grayscale to a JPanel does not work

SamuelXiao <>
Wed, 9 Feb 2011 20:12:10 -0800 (PST)
On Feb 10, 9:48 am, Knute Johnson <> wrote:

On 02/09/2011 09:17 AM, SamuelXiao wrote:

On Feb 10, 12:37 am, Knute Johnson<> wrote:

On 02/09/2011 07:29 AM, SamuelXiao wrote:

On Feb 9, 10:50 pm, "John B. Matthews"<nos...@nospam.invalid> =


In article

   SamuelXiao<> wrote:

I currently paint line chart/bar chart to there (the drawing area
painting line chart/bar chart).
In addition, I have tried the example in



but it does not work as well.

This is the very code I was going to suggest; it works correctly for
me. Are you having trouble converting your chart to a BufferedImage?
I don't know how you create your chart, but org.jfree.chart.JFreeCha=


includes suitable methods.

Any help would be highly appreciated.

John B. Matthews
trashgod at gmail dot com

Hi, the code converts an imaged to grayscale. but for my situation, I
need to converts Graphics in an applet (lines, rectangels, string) to
grayScale. The paint method in my Applet is like:

public void paint(Graphics g){
    Graphics2D g2d = (Graphics2D) g;



    case 0:
    case 1:

But it does not work as the example. It just paint another rectangle
with gray color on top of those line/string/so on. Do you have any
idea for it? Thanks.

     public static BufferedImage convertToGray(BufferedImage ima=

ge) {

          BufferedImage gray = new BufferedImage(image.get=




          ColorConvertOp op = new ColorConvertOp(
          return gray;

Knute Johnson

Hi, I tried the code but still the same. I first make the drawing area
in JPanel become a bufferedimage. Then calls the above function and
finally drawImage, but it will return a gray rectangle as well. Below
is the showGrayScale function.

private void showGrayScale(Graphics2D g2d){
   int pre_height = 29;
         // a region in JPanel become a bufferedimage.
   BufferedImage img = new BufferedImage(getWidth(),
                   getHeight()-pre_height, Buffered=


   BufferedImage gray = convertToGray(img);


and in fact, in the paint function:
public void paint(Graphics g){
   Graphics2D g2d = (Graphics2D) g;



         case 0:
         case 1:


it will first paint showLineChart(g2d) which is a function paint line
chart using drawLine and each line has different color. The Rectangle
was at the right position but doesn't grayscale those line chart. Does
I miss something here? Thanks.

You need to send us more than just pieces of code. We really need to
see an SSCCE if you want good help.

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

public class GreyTest extends JPanel implements ActionListener {
     private final BufferedImage color,gray;
     boolean flag = true;

     public GreyTest() {
         setPreferredSize(new Dimension(400,300));
         color = new BufferedImage(400,300,BufferedImage.TYPE=


         Graphics2D g = color.createGraphics();
         gray = convertToGray(color);

     public void actionPerformed(ActionEvent ae) {
         flag = !flag;

     public void paintComponent(Graphics g) {
         if (flag)

     static BufferedImage convertToGray(BufferedImage image) {
         BufferedImage gray = new BufferedImage(image.getWidt=


         ColorConvertOp op = new ColorConvertOp(
         return gray;

     public static void main(String[] args) {
         EventQueue.invokeLater(new Runnable() {
             public void run() {
                 JFrame f = new JFrame("Grey Test");


                 GreyTest gt = new GreyTest();
                 JButton b = new JButton("Color/Grey"=





Knute Johnson

Thanks all, the grayscale problem was solved. And then I found another
big problem for the color scheme, option 1 use grayscale(solved) but
option 2 high contrast & option 3 winter color. option 2 is ok for me
but for option 3, I found it cannot use the same approach to solve
it. Then now I hard code colorscheme for each option, including
grayscale, high contrast. I set those graphics line/rectanges with
different color instead of the whole area. The problem is also solved
now. But I wonder if there is any approach to set buffered image with
Winter color???

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