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Groups > comp.lang.java.gui > #4986

Re: How do I paint on an existing Panel?

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On 18/01/2012 16:55, A B wrote:
> I expect this is a really obvious question; I must get round to getting
> a bigger Java book! Part of my program starts by displaying a JPanel,
> with an image put on it using paintComponent(). How do I then draw some
> shapes over the top of that image when a particular button is clicked? I
> can't just put them in paintComponent(), because they haven't to appear
> at first. Would it be easier in an applet, rather than an application?
>
> I'm sure this comes up in the example programs in the JDK package, but
> for some mysterious reason they won't work. Wrong version of IE,
> probably; have to look into that.
>
HI

I had the same problem! my solution is as follows


/*
  * To change this template, choose Tools | Templates
  * and open the template in the editor.
  */
package imagelibrary;

//~--- JDK imports 
------------------------------------------------------------
import java.awt.Dimension;
import java.awt.Graphics;
import java.awt.LayoutManager;
import java.awt.image.BufferedImage;
import java.io.File;
import java.io.FileInputStream;
import java.io.IOException;
import javax.imageio.ImageIO;
import java.io.InputStream;
import javax.swing.JPanel;

/**
  *
  * @author NeilLewisMorris
  */
public class ImagePanel extends JPanel {

     private BufferedImage Bimage = null;
     private File imageFile = null;
     private InputStream imageInputStream = null;
     private Dimension size;
     private double panelWidth;
     private double panelHeight;
     private double BimageWidth;
     private double BimageHeight;
     private double scaledWidth;
     private double scaledHeight;
     private double scaled;
     private double startX = 0;
     private double startY = 0;

     public ImagePanel() {
         super();
     }

     public ImagePanel(LayoutManager layout) {
         super(layout);
     }

     @Override
     public void paintComponent(Graphics g) {
         super.paintComponent(g);
         if (Bimage != null) {
             BimageWidth = Bimage.getWidth();
             BimageHeight = Bimage.getHeight();
             panelWidth = getWidth();
             panelHeight = getHeight();
             scaledWidth = panelWidth / BimageWidth;
             scaledHeight = panelHeight / BimageHeight;

             if (scaledWidth > scaledHeight) {
                 scaled = scaledHeight;
             } else {
                 scaled = scaledWidth;
             }
             scaledWidth = scaled * BimageWidth;
             scaledHeight = scaled * BimageHeight;
             startX = (panelWidth - scaledWidth) / 2;
             startY = (panelHeight - scaledHeight) / 2;
         } else {
             scaledWidth = 0;
             scaledHeight = 0;
         }
         if (Bimage != null) {
             g.drawImage(Bimage, (int)startX, (int)startY, (int) 
scaledWidth, (int) scaledHeight, this);
         }
     }

     public File getImageFile() {
         return imageFile;
     }

     public boolean setImageFile(File file) throws IOException {
         imageFile = file;
         return setImageInputStream(new FileInputStream(imageFile));
     }

     public boolean setImageInputStream(InputStream inputstream) {
         imageInputStream = inputstream;
         try {
             Bimage = ImageIO.read(imageInputStream);
         } catch (IOException e) {
             return false;
         }
         revalidate();
         repaint();
         return true;
     }
}

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Thread

How do I paint on an existing Panel? "A B" <@bleBaker.uk> - 2012-01-18 16:55 +0000
  Re: How do I paint on an existing Panel? Knute Johnson <nospam@knutejohnson.com> - 2012-01-18 09:29 -0800
    Re: How do I paint on an existing Panel? "A B" <@bleBaker.uk> - 2012-01-18 18:12 +0000
      Re: How do I paint on an existing Panel? Knute Johnson <nospam@knutejohnson.com> - 2012-01-18 15:00 -0800
  Re: How do I paint on an existing Panel? markspace <-@.> - 2012-01-18 10:55 -0800
  Re: How do I paint on an existing Panel? Roedy Green <see_website@mindprod.com.invalid> - 2012-01-20 19:54 -0800
  Re: How do I paint on an existing Panel? "A B" <@bleBaker.uk> - 2012-01-30 17:59 +0000
  Re: How do I paint on an existing Panel? Neil Morris <neil.morris4@googlemail.com> - 2012-02-04 20:58 +0000
    Re: How do I paint on an existing Panel? Lew <lewbloch@gmail.com> - 2012-02-05 01:01 -0800
    Re: How do I paint on an existing Panel? "A B" <@bleBaker.uk> - 2012-02-10 12:10 +0000
    Re: How do I paint on an existing Panel? "A B" <@bleBaker.uk> - 2012-02-16 20:55 +0000
      Re: How do I paint on an existing Panel? Lew <lewbloch@gmail.com> - 2012-02-16 13:04 -0800
        Re: How do I paint on an existing Panel? "A B" <@bleBaker.uk> - 2012-02-16 21:33 +0000
  Re: How do I paint on an existing Panel? "A B" <@bleBaker.uk> - 2012-02-16 21:05 +0000
    Re: How do I paint on an existing Panel? Lew <lewbloch@gmail.com> - 2012-02-16 13:28 -0800
      Re: How do I paint on an existing Panel? "John B. Matthews" <nospam@nospam.invalid> - 2012-02-16 21:18 -0500
      Re: How do I paint on an existing Panel? "A B" <@bleBaker.uk> - 2012-02-17 18:20 +0000
        Re: How do I paint on an existing Panel? Lew <lewbloch@gmail.com> - 2012-02-17 10:45 -0800
        Re: How do I paint on an existing Panel? Lew <lewbloch@gmail.com> - 2012-02-17 10:49 -0800
          Re: How do I paint on an existing Panel? "A B" <@bleBaker.uk> - 2012-02-19 19:31 +0000
            Re: How do I paint on an existing Panel? Lew <noone@lewscanon.com> - 2012-02-19 14:41 -0800
              Re: How do I paint on an existing Panel? "A B" <@bleBaker.uk> - 2012-03-04 16:51 +0000
                Re: How do I paint on an existing Panel? Jeff Higgins <jeff@invalid.invalid> - 2012-03-04 12:36 -0500
                Re: How do I paint on an existing Panel? Lew <noone@lewscanon.com> - 2012-03-04 10:47 -0800
                Re: How do I paint on an existing Panel? "A B" <@bleBaker.uk> - 2012-03-14 17:39 +0000
                Re: How do I paint on an existing Panel? Lew <lewbloch@gmail.com> - 2012-03-14 11:07 -0700
                Re: How do I paint on an existing Panel? "John B. Matthews" <nospam@nospam.invalid> - 2012-03-14 23:01 -0400
                Re: How do I paint on an existing Panel? markspace <-@.> - 2012-03-15 09:30 -0700
        Re: How do I paint on an existing Panel? Knute Johnson <nospam@knutejohnson.com> - 2012-02-17 17:01 -0800
    Re: How do I paint on an existing Panel? Knute Johnson <nospam@rabbitbrush.frazmtn.com> - 2012-02-16 13:59 -0800
      Re: How do I paint on an existing Panel? "A B" <@bleBaker.uk> - 2012-02-17 18:07 +0000
        Re: How do I paint on an existing Panel? Knute Johnson <nospam@knutejohnson.com> - 2012-02-17 17:04 -0800
        Re: How do I paint on an existing Panel? Knute Johnson <nospam@knutejohnson.com> - 2012-02-17 17:08 -0800

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