Dynamically resize a bufferedimage in java

Question

I tried resizing the buffered image using AffineTransform as well as Scalr.resize

Here are my codes for both of them.

using Scalr.resize:

    BufferedImage buff = robot.createScreenCapture(new Rectangle(bufx,bufy,bufwidth,bufheight)); // x-coord, y-coord, width, height

    BufferedImage scrCapt = Scalr.resize(buff, Method.BALANCED, scrwidth, scrheight);

using AffineTransform:

BufferedImage buff = robot.createScreenCapture(new Rectangle(bufx,bufy,bufwidth,bufheight)); // x-coord, y-coord, width, height

BufferedImage scrCapt = new BufferedImage(bufwidth,bufheight,BufferedImage.TYPE_INT_ARGB);
AffineTransform atscr = new AffineTransform();


atscr.scale(aspectRatioWidth,aspectRatioHeight);
AffineTransformOp scaleOp = new AffineTransformOp(atscr, AffineTransformOp.TYPE_BILINEAR);
scrCapt = scaleOp.filter(buff, scrCapt);

the variables have been declared in the beginning inside class:

static int bufx = 0;
static int bufy = 0;
static int bufwidth = 1;
static int bufheight = 1;
static int scrwidth = 0;
static int scrheight = 0;
static float aspectRatioWidth = 0;
static float aspectRatioHeight = 0;

I am getting the values for for all the variables dynamically inside a different method:

aspectRatioWidth = bufwidth/scrwidth;
aspectRatioHeight = bufheight/scrheight;

However when I run this code I get an error in both the functions AffineTransform as well as Scalr.resize:

Scalr.resize:

Exception in thread "Thread-2" java.lang.IllegalArgumentException: Width (0) and height (0) cannot be <= 0
at java.awt.image.DirectColorModel.createCompatibleWritableRaster(DirectColorModel.java:1016)
at java.awt.image.BufferedImage.<init>(BufferedImage.java:331)
at org.imgscalr.Scalr.createOptimalImage(Scalr.java:2006)
at org.imgscalr.Scalr.scaleImage(Scalr.java:2133)
at org.imgscalr.Scalr.resize(Scalr.java:1667)
at org.imgscalr.Scalr.resize(Scalr.java:1415)

AffineTransform:

Exception in thread "Thread-2" java.awt.image.ImagingOpException: Unable to invert transform AffineTransform[[0.0, 0.0, 0.0], [0.0, 1.0, 0.0]]
at java.awt.image.AffineTransformOp.validateTransform(AffineTransformOp.java:558)
at java.awt.image.AffineTransformOp.<init>(AffineTransformOp.java:151)

How do I go about this? I understand that this is happening because I am changing the variable in a different method and accessing them in another one. But those two methods can't be combined. Is there any way I can make this work?

EDIT:

I changed the method of resizing Here's what I did now

public static BufferedImage resizeImage(BufferedImage image, double scalewidth, double scaleheight){

    BufferedImage img = new BufferedImage(image.getWidth(), image.getHeight(),BufferedImage.SCALE_FAST);
    Graphics2D g = img.createGraphics();
    g.scale(scalewidth, scaleheight);
    g.drawImage(image, null, 0, 0);
    g.dispose();
    return image;
}

EDIT(2):

For a clearer idea of what is happening exactly:

This is a method which returns scrwidth and scrheight

public static void showOnScreen( int screen, JFrame framenew )
   {
    GraphicsEnvironment ge = GraphicsEnvironment
      .getLocalGraphicsEnvironment();
    GraphicsDevice[] gs = ge.getScreenDevices();

  for (int i = 0; i < gs.length; i++) {
      screenwidth.add(gs[i].getDisplayMode().getWidth());
      screenheight.add(gs[i].getDisplayMode().getHeight());
}

scrwidth = screenwidth.get(screenwidth.size()-1);
scrheight = screenheight.get(screenheight.size()-1);




  System.out.print(ge);
  System.out.print(gs);
  if( screen > -1 && screen < gs.length )
  {gs[screen].setFullScreenWindow( framenew );}
  else if( gs.length > 0 )
  {gs[0].setFullScreenWindow( framenew );}
  else
  {throw new RuntimeException( "No Screens Found" );}}

And this is the actionlistener which returns bufwidth and bufheight:

  btnNewButton.addActionListener(new ActionListener() {      
  public void actionPerformed(ActionEvent e)
  {
      //Execute when button is pressed
      System.out.println("You clicked the button");

      int ind = c.getSelectedIndex();
        bufx = capx.get(ind);
        bufy = capy.get(ind);
        bufwidth = capwidth.get(ind);
        bufheight = capheight.get(ind);
        frame.setVisible(false);
        framenew.setVisible(true);
        showOnScreen(1,framenew);

        aspectRatioWidth = (double) bufwidth/scrwidth;
        aspectRatioHeight = (double) bufheight/scrheight;   

            System.out.print("aspectRatioWidth:  ");
            System.out.println(aspectRatioWidth);

            System.out.print("aspectRatioHeight:  ");
            System.out.println(aspectRatioHeight);          
  }
  });      

And aspectRatios are used inside run:

public void run() {
System.out.print("aspectRatioWidth:  ");
System.out.println(aspectRatioWidth);

System.out.print("aspectRatioHeight:  ");
System.out.println(aspectRatioHeight);

while(true){
    BufferedImage buff = robot.createScreenCapture(new Rectangle(bufx,bufy,bufwidth,bufheight)); // x-coord, y-coord, width, height

    BufferedImage resizedbuff = resizeImage(buff, aspectRatioWidth, aspectRatioHeight);}

Answer 1

You're doing int division which always returns an int, here 0 since your screen dimensions will likely be greater than your image dimensions:

aspectRatioWidth = bufwidth/scrwidth;
aspectRatioHeight = bufheight/scrheight;

Solution: convert the numbers to double and then do double division.

aspectRatioWidth = (double) bufwidth/scrwidth;
aspectRatioHeight = (double) bufheight/scrheight;

---

Edit

Not sure what you're ultimately trying to do -- post the image of the computer screen in your GUI? If so, perhaps something like...

import java.awt.AWTException;
import java.awt.Dimension;
import java.awt.Graphics;
import java.awt.Rectangle;
import java.awt.Robot;
import java.awt.Toolkit;
import java.awt.event.WindowAdapter;
import java.awt.event.WindowEvent;
import java.awt.geom.AffineTransform;
import java.awt.image.AffineTransformOp;
import java.awt.image.BufferedImage;
import java.util.List;

import javax.swing.*;

public class ChangeVars extends JPanel {
   private static final int PREF_W = 400;
   private static final int PREF_H = PREF_W;
   private static final int DELAY = 20;
   public BufferedImage displayImage;
   private MyWorker myWorker;

   public ChangeVars() {
      try {
         myWorker = new MyWorker(DELAY);
         myWorker.execute();
      } catch (AWTException e) {
         e.printStackTrace();
      }
   }

   @Override
   // to initialize the panel to something
   public Dimension getPreferredSize() {
      if (isPreferredSizeSet()) {
         return super.getPreferredSize();
      }
      return new Dimension(PREF_W, PREF_H);
   }

   @Override
   protected void paintComponent(Graphics g) {
      super.paintComponent(g);
      if (displayImage != null) {
         g.drawImage(displayImage, 0, 0, null);
      }
   }

   public void stopWorker() {
      if (myWorker != null && !myWorker.isDone()) {
         myWorker.setRunning(false);
         myWorker.cancel(true);
      }
   }

   private class MyWorker extends SwingWorker<Void, BufferedImage> {

      private volatile boolean running = true;
      private Robot robot;
      private int delay;

      public MyWorker(int delay) throws AWTException {
         this.delay = delay;
         robot = new Robot();
      }

      @Override
      protected Void doInBackground() throws Exception {
         while (running) {
            Dimension d = Toolkit.getDefaultToolkit().getScreenSize();
            Rectangle screenRect = new Rectangle(0, 0, d.width, d.height);
            BufferedImage img = robot.createScreenCapture(screenRect);
            publish(img);
            Thread.sleep(delay);
         }
         return null;
      }

      @Override
      protected void process(List<BufferedImage> chunks) {
         for (BufferedImage image : chunks) {
            Dimension sz = getSize();
            double scaleX = (double) sz.width / image.getWidth();
            double scaleY = (double) sz.height / image.getHeight();
            AffineTransform transform = AffineTransform.getScaleInstance(
                  scaleX, scaleY);
            AffineTransformOp transformOp = new AffineTransformOp(transform,
                  AffineTransformOp.TYPE_BILINEAR);
            displayImage = new BufferedImage(sz.width, sz.height,
                  BufferedImage.TYPE_INT_ARGB);
            displayImage = transformOp.filter(image, displayImage);
            repaint();
         }
      }

      public void setRunning(boolean running) {
         this.running = running;
      }

      public boolean getRunning() {
         return running;
      }

   }

   private static void createAndShowGui() {
      final ChangeVars changeVars = new ChangeVars();

      JFrame frame = new JFrame("ChangeVars");
      frame.setDefaultCloseOperation(JFrame.DO_NOTHING_ON_CLOSE);
      frame.addWindowListener(new WindowAdapter() {

         @Override
         public void windowClosing(WindowEvent e) {
            if (changeVars != null) {
               changeVars.stopWorker();
            }
            System.exit(0);
         }

      });
      frame.getContentPane().add(changeVars);
      frame.pack();
      frame.setLocationByPlatform(true);
      frame.setVisible(true);
   }

   public static void main(String[] args) {
      SwingUtilities.invokeLater(new Runnable() {
         public void run() {
            createAndShowGui();
         }
      });
   }
}

Although simpler would be to just let paintComponent do the scaling:

@Override
protected void paintComponent(Graphics g) {
  super.paintComponent(g);
  if (displayImage != null) {
     int width = getWidth();
     int height = getHeight();
     g.drawImage(displayImage, 0, 0, width, height, null);
  }
}

// ....

  @Override
  protected void process(List<BufferedImage> chunks) {
     for (BufferedImage image : chunks) {
        displayImage = image;
        repaint();
     }
  }