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;
}
}
Thanks, that's handy! I'll try it out.
A. B.
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