Glitches with painting a component into an image, with AffineTransform
I made the test program below. I want to create an image out of a component, that has some random lines painted on it. Running the program and pushing the button will create a file "out.png".
The component has original size (4000,4000). I try to scale it down with AffineTransform, applied into the image's Graphics object.The lines do not appear correctly. The seem just like when you have animage with lines, and produce a quick thumbnail out of it. But I don't understand why this is happening. I actually draw lines with an AffineTransform, so I would expect that a line will be drawn in merely different coordinates.
Why the lines fail to appear correctly?
And a side issue. When I scroll, the component fails to repaint appropriately, I'm seeing visual remains of previous paints. Why does this happen?
Here is the code, run under 1.6:
//ImageTest.java
import java.awt.BorderLayout;
import java.awt.Component;
import java.awt.Dimension;
import java.awt.Graphics;
import java.awt.Graphics2D;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.awt.geom.AffineTransform;
import java.awt.image.BufferedImage;
import java.io.File;
import java.io.IOException;
import java.util.Random;
import javax.imageio.ImageIO;
import javax.swing.JButton;
import javax.swing.JFrame;
import javax.swing.JPanel;
import javax.swing.JScrollPane;
/**
*
* @author andreou
*/
publicclass ImageTestextends JFrame{
privatefinal Component c;
public ImageTest(){
c =new MyComponent();
add(new JScrollPane(c));
JButton button =new JButton("save");
button.addActionListener(new ActionListener(){
publicvoid actionPerformed(ActionEvent e){
save();
}
});
add(button, BorderLayout.NORTH);
}
privatevoid save(){
BufferedImage bi = (BufferedImage)c.createImage(c.getWidth(), c.getHeight());
Graphics2D g = (Graphics2D)bi.getGraphics();
double w = 800;
double h = 800;
g.setTransform(AffineTransform.getScaleInstance(w / c.getWidth(), h / c.getHeight()));
c.paint(g);
g.dispose();
try{
ImageIO.write(bi,"png",new File("out.png"));
}catch (IOException ex){
ex.printStackTrace();
}
}
publicstaticvoid main(String[] args){
JFrame f =new ImageTest();
f.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
f.setSize(400, 400);
f.setLocationRelativeTo(null);
f.setVisible(true);
}
}
class MyComponentextends JPanel{
privatefinal Random random =new Random();
{
setPreferredSize(new Dimension(4000, 4000));
}
publicvoid paintComponent(Graphics g){
Random r =new Random(0);
for (int i = 0; i < 1000; i++){
g.drawLine(nextX(r), nextY(r), nextX(r), nextY(r));
}
}
privateint nextX(Random random){
return random.nextInt(getWidth());
}
privateint nextY(Random random){
return random.nextInt(getHeight());
}
}
Thanks a lot for any help
