Re: color space conversions

From:

patriarch24 <cyril.delmas@gmail.com>

Newsgroups:

comp.lang.java.programmer

Date:

Thu, 12 Jun 2008 09:08:20 -0700 (PDT)

Message-ID:

<1f9aaa09-dbdd-4b4a-92c2-3269f5a6575c@f63g2000hsf.googlegroups.com>

This seems interesting, thank you. But it converts to grayscale image,
which is a current use case (I think I have found billions code
samples for that). Converting from rgb to cmyk or from cmyk to rgb
really seems to be a hard question (resulting images are too bright or
too dark depending on the direction in my samples).
Any other suggestion ?

Here is a simple program that reads a color image and converts it to
grayscale using ColorConvertOp. Using this as a sample you should be
able to convert anything. I wrote this for a fellow that wanted to draw
a transparent color image over a grayscale image but the ColorConvertOp
is what you are interested in.

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

public class test6 extends JPanel {
     BufferedImage image;
     BufferedImage gray;
     BufferedImage color;

     public test6() {
         setPreferredSize(new Dimension(400,300));
         try {
             // read an image from the disk
             image = ImageIO.read(new File("kittens.jpg"));

             // create a grayscale image the same size
             gray = new BufferedImage(image.getWidth(),image.getHeight(),
              BufferedImage.TYPE_BYTE_GRAY);

             // create a color image with alpha for output
             color = new BufferedImage(400,300,BufferedImage.TYPE_INT_ARGB);

             // convert the original colored image to grayscale
             ColorConvertOp op = new ColorConvertOp(
              image.getColorModel().getColorSpace(),
              gray.getColorModel().getColorSpace(),null);
             op.filter(image,gray);

             // draw the grayscale image on the output image
             Graphics g = color.getGraphics();
             g.drawImage(gray,0,0,null);

             // draw some transparent blue pixels over the whole image
             g.setColor(new Color(0,0,255,80));
             g.fillRect(0,0,400,300);
         } catch (IOException ioe) {
             ioe.printStackTrace();
         }
     }

     public void paintComponent(Graphics g) {
         g.drawImage(color,0,0,null);
     }

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

                 test6 t6 = new test6();
                 f.add(t6,BorderLayout.CENTER);
                 f.pack();
                 f.setVisible(true);
             }
         });
     }

}

--

Knute Johnson
email s/nospam/knute2008/

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