SetRGB being capricious

Question

Hi, I have a 4 channel 8 bit greyscale image (the alpha channel=0) and I am trying to adjust the image so that
the Chroma and Luma values are altered for certain regions.
For instance, looping over the width and height, obtained from a Buffered Image, I have the following:
if ( width> 634 && width<764 && height>259 && height<350 ) //light blue
                    Cb=133;
                    Cr=124;
                    int myR = (selectedColour >> 16) & 0xff;
                    int Y= myR; // only need the greyscale: in such an image, red=green=blue
                        int [] rgb = ycbcr2rgb(Y, Cb, Cr);
                    int a = 0;
                         int r = rgb[0];
                         int g = rgb[1];
                         int b = rgb[2];
                               // Now we add the colour.....
                    int newcolour = a << 24 | r << 16 | g << 8 | b;
                    bufferedImage.setRGB(width, height, newcolour );
               }And I have
public int [] ycbcr2rgb(int y, int cb, int cr)
          int r = (int)( 1.164*(y-16) + 1.596*(cr-128) );
          int g = (int)( 1.164*(y-16) - 0.392*(cb-128) -0.813*(cr-128));
          int b = (int)( 1.164*(y-16) + 2.017*(cb-128) );
          int [] rgb = new int[3];
          rgb[0] = r;
          rgb[1] = g;
          rgb[2] = b;
          return rgb;       
}I am sure that ycbcr2rgb is returning meaningful results as I have checked them, and I am sure that variables such as "newcolour" are being set correctly, but it doesn't alter the colours in the Buffered Image correctly. All the areas are white, with faint traces of bright yellow, whereas they should be in this example, a light blue shade. Am I missing something very obvious here?
Thanks!
Paul
Edited by: [email protected] on Jul 20, 2010 6:59 PM - got over zealous with the tab key.

Answer 1

Hi,
I've tried that but with no luck. As requested, I've attached a highly slimmed down copy of my code, removing some of the text boxes to show RGB, YCbCr when the mouse moves over a position etc.
import javax.swing.*;
import java.awt.*;
import java.awt.event.*;
import java.util.*;
import java.lang.*;
import java.lang.Math.*;
import java.io.File;
import javax.imageio.ImageIO;
import java.awt.image.BufferedImage;
public class ColourOverlay extends JFrame
     JMenu Items;
     JMenuItem openFile, convert;
     imgDisplay chromaImg;
     JFileChooser fileChooser;
     public static void main( String args[] )
          ColourOverlay application = new ColourOverlay();
     public ColourOverlay()
          Items = new JMenu( "Items" );
          openFile = new JMenuItem("Open");
          convert = new JMenuItem("Convert");
          Items.add( openFile );
          Items.add( convert );
          openFile.addActionListener(
               new ActionListener()
                    public void actionPerformed( ActionEvent e )
                         openFile();
          convert.addActionListener(
               new ActionListener()
                    public void actionPerformed( ActionEvent e )
                         convert();
          JMenuBar bar = new JMenuBar();
          setJMenuBar ( bar );
          bar.add( Items );
          chromaImg = new imgDisplay( this );
          getContentPane().setLayout(
    new BoxLayout(getContentPane(), BoxLayout.PAGE_AXIS)
          add( chromaImg );
             pack();
             setVisible(true);
     private void openFile()
          fileChooser = new JFileChooser();
          fileChooser.setFileSelectionMode ( JFileChooser.FILES_ONLY );
          int result = fileChooser.showOpenDialog( this );
          File filename = fileChooser.getSelectedFile();
          try
               chromaImg.setBufferedImage(ImageIO.read(filename));
          catch (Exception exception)
                        exception.printStackTrace();
          chromaImg.repaint();
          chromaImg.resize();
     private void convert()
          chromaImg.convert();
          chromaImg.repaint();
class imgDisplay extends JPanel
     private BufferedImage bufferedImage;
     private Dimension PanelDimension = new Dimension();
     private ColourOverlay CA;
     public imgDisplay( ColourOverlay CA )
          this.CA = CA;
     addMouseMotionListener
          new MouseMotionListener()
               public void mouseMoved( MouseEvent event )
                    processMouseMove( event );
               public void mouseDragged( MouseEvent event )
     public void setBufferedImage(BufferedImage bufferedImage)
        this.bufferedImage = bufferedImage;
     public BufferedImage getBufferedImage()
        return bufferedImage;
     public void resize()
        PanelDimension.setSize(bufferedImage.getWidth(), bufferedImage.getHeight());
        setPreferredSize(PanelDimension);          
    protected void paintComponent(Graphics g)
        super.paintComponent(g);
        g.drawImage(bufferedImage, 0, 0, this);
     public void convert()
          if ( bufferedImage == null ) return;
          for(int height=0; height < bufferedImage.getHeight(); height++)
               for(int width=0; width < bufferedImage.getWidth(); width++)
                    int selectedColour = bufferedImage.getRGB( width, height );
               int Cb, Cr;
               if ( width> 247 && width<295 && height>341 && height<413 ) //pink
                    Cb=116;
                    Cr=149;
                    int myR = (selectedColour >> 16) & 0xff;
                    int Y= myR;
                        int [] rgb = ycbcr2rgb(Y, Cb, Cr);
                    int a = 0;
                         int r = rgb[0];
                         int g = rgb[1];
                         int b = rgb[2];
                    int newcolour = a << 24 | r << 16 | g << 8 | b;
                    bufferedImage.setRGB(width, height, newcolour );
               if ( width> 219 && width<388 && height>462 && height<506 ) //red
                    Cb=125;
                    Cr=155;
                    int myR = (selectedColour >> 16) & 0xff;
                    int Y= myR;
                        int [] rgb = ycbcr2rgb(Y, Cb, Cr);
                    int a = 0;
                         int r = rgb[0];
                         int g = rgb[1];
                         int b = rgb[2];
                    int newcolour = a << 24 |r << 16 | g << 8 | b;
                    bufferedImage.setRGB(width, height, newcolour );
               if ( width> 634 && width<764 && height>259 && height<350 ) //light blue
                    Cb=133;
                    Cr=124;
                    int myR = (selectedColour >> 16) & 0xff;
                    int Y= myR;
                        int [] rgb = ycbcr2rgb(Y, Cb, Cr);
                    int a = 0;
                         int r = rgb[0];
                         int g = rgb[1];
                         int b = rgb[2];
                    int newcolour = a << 24 | r << 16 | g << 8 | b;
                    bufferedImage.setRGB(width, height, newcolour );
     private void processMouseMove( MouseEvent event )
public int [] rgb2ycbcr(int r, int g, int b)
          int y = (int) (16 + 0.257*r + 0.504*g + 0.098*b);
          int cb = (int) (128 - 0.148*r - 0.291*g + 0.439*b);
          int cr = (int) (128 + 0.439*r -0.368*g -0.071*b);
          int [] ycbcr = new int[3];
          ycbcr[0] = y;
          ycbcr[1] = cb;
          ycbcr[2] = cr;
          return ycbcr;       
public int [] ycbcr2rgb(int y, int cb, int cr)
          int r = (int)( 1.164*(y-16) + 1.596*(cr-128) );
          int g = (int)( 1.164*(y-16) - 0.392*(cb-128) -0.813*(cr-128));
          int b = (int)( 1.164*(y-16) + 2.017*(cb-128) );
          int [] rgb = new int[3];
          rgb[0] = r;
          rgb[1] = g;
          rgb[2] = b;
          return rgb;       
}The image I have been fiddling with is on my website http://www.paullee.com/main.png
- what should happen is the test rectangle to the lower left should be a dark maroon colour, the rectangle to
the right should be a grey-light blue colour, and the one in between should be vaguely flesh coloured (but could be any colour between tan and orange)
Thanks for your help
Paul