Re: Select an area of an image...
RichT wrote:
Hi,
I am struggling to find an algorithm that will allow to select an area
of an image, scale it to fir the size of the window and centre it.
I can zoom in and out of an image where the entire zoomed image is
centred and scaled.
If I have a viewing area of 640 X 400, an image twice this size and
centred, now if I select an area using a selection rectangle at location
say 150, 40 with a width of 60 and a height 35, how can I scale this
area say by a factor of eight and centre it?
I am using an AffineTransform for the zoom in and out to scale and
translate and draw the entire image (in the JComponent) so that it is
displayed in the centre of the window (a JComponent in a JFrame).
I am guessing this involves changing the origin of the image.
I would really appreciate some pointer or help here
Thanks in advance
RT
I wrote the CropComponent a few months ago for somebody else on this
list. It is a simple example of how to select an area of an existing
image and crop out a subimage. Once you have the subimage it is trivial
to scale and center it. If you are trying to both scale and crop at the
same time it will probably be more complex. Maybe drawing the subimage
in its own component or in another frame may be easier. Without a more
detailed description of what you want to do it is difficult to help.
import java.awt.*;
import java.awt.event.*;
import java.awt.image.*;
import java.io.*;
import java.net.*;
import javax.imageio.*;
import javax.swing.*;
public class CropComponent extends JPanel {
BufferedImage bi,subImage;
boolean mouseDown;
int startX,startY;
int endX,endY;
int x,y,w,h;
public CropComponent(BufferedImage bi) {
this.bi = bi;
setPreferredSize(new Dimension(bi.getWidth(),bi.getHeight()));
addMouseListener(new MouseAdapter() {
public void mousePressed(MouseEvent me) {
mouseDown = true;
startX = me.getX();
startY = me.getY();
}
public void mouseReleased(MouseEvent me) {
mouseDown = false;
subImage = CropComponent.this.bi.getSubimage(x,y,w+1,h+1);
Runnable r = new Runnable() {
public void run() {
try {
ImageIO.write(subImage,"JPEG",new
File("crop.jpg"));
} catch (IOException ioe) {
ioe.printStackTrace();
}
}
};
new Thread(r).start();
x = y = w = h = 0;
repaint();
}
});
addMouseMotionListener(new MouseMotionAdapter() {
public void mouseDragged(MouseEvent me) {
endX = Math.max(0,me.getX());
endX =
Math.min(endX,CropComponent.this.bi.getWidth()-1);
endY = Math.max(0,me.getY());
endY =
Math.min(endY,CropComponent.this.bi.getHeight()-1);
if (startX < endX && startY < endY) {
x = startX;
y = startY;
w = endX-startX;
h = endY-startY;
} else if (startX > endX && startY > endY) {
x = endX;
y = endY;
w = startX-endX;
h = startY-endY;
} else if (startX < endX && startY > endY) {
x = startX;
y = endY;
w = endX-startX;
h = startY-endY;
} else if (startX > endX && startY < endY) {
x = endX;
y = startY;
w = startX-endX;
h = endY-startY;
}
repaint();
}
});
}
public void paintComponent(Graphics g2D) {
Graphics2D g = (Graphics2D)g2D;
g.drawImage(bi,0,0,null);
if (mouseDown) {
g.setStroke(new BasicStroke(1.0f,BasicStroke.CAP_SQUARE,
BasicStroke.JOIN_ROUND,1.0f,new float[] {2.0f,3.0f},1.0f));
g.setColor(Color.WHITE);
g.drawRect(x,y,w,h);
}
}
public static void main(final String[] args) {
Runnable r = new Runnable() {
public void run() {
BufferedImage bi = null;
try {
try {
bi = ImageIO.read(new URL(args[0]));
} catch (MalformedURLException murle) {
bi = ImageIO.read(new File(args[0]));
}
JFrame f = new JFrame();
f.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
CropComponent cc = new CropComponent(bi);
JScrollPane sp = new JScrollPane(cc);
f.add(sp,BorderLayout.CENTER);
f.pack();
f.setVisible(true);
} catch (IOException ioe) {
ioe.printStackTrace();
}
}
};
EventQueue.invokeLater(r);
}
}
--
Knute Johnson
email s/nospam/linux/
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