Generate a JPEG file

Question

In my project, I need to generate a JPEG file in using a screen capture that I obtain with the use of a Robot.
I have the following code :
public static BufferedImage getScreenCapture(int x, int y, int width, int height)
     Robot            robot            = null;
     Rectangle        rectangle        = null;
     BufferedImage    bufferedImage    = null;
     try
          robot = new Robot();
          rectangle     = new Rectangle(x, y, width, height);
          bufferedImage = robot.createScreenCapture(rectangle);
     catch(Exception e)
          e.printStackTrace();
     finally
          return bufferedImage;
}After the load of my buffered image, I need to generate the JPEG file. So, I use the following code :
try
     JPEGEncodeParam  jpegEncodeParam  = null;
     JPEGImageEncoder jpegImageEncoder = null;
     BufferedImage bufferedImage = ImageManager.getScreenCapture(0, 0, 100, 100);
     jpegEncodeParam  = JPEGCodec.getDefaultJPEGEncodeParam(bufferedImage);
     jpegImageEncoder = JPEGCodec.createJPEGEncoder(new FileOutputStream( new File("C:\\test.jpg") ), jpegEncodeParam);
catch(Exception e)
     e.printStackTrace();
}The result of this is that I've got a jpeg file empty.
I'm novice in the use of the Codec, so my question is maybe stupid but I don't understand where is my error.
If someone can help me.

Answer 1

I Don't understand the codec either and have ahard time understanding the docs on JAI and ImageIO
compared to the rest of Java.
However the below code does write out a JPEG file, that can be viewed by Java and other Image Viewers,.
I'd say check if your "Robot" ???? is actually getting an Image, by subclasssing ImageIcon to show a
BufferedImage and sticking that on A JLabel ??
I'd like to see the 'correct' way to do this so you can set all the parameters, but if you just want a jpeg file adapt this:
Err it loads in a tif image off disk and writes it out in all the supported formats
( at least I think it does )
import javax.imageio.*;
import java.awt.Dimension;
import java.util.*;
import java.lang.*;
import java.io.*;
import java.awt.image.*;
public class ReadWriteTest
     private String ErrorString;
     private boolean SuccessStatus;
     private BufferedImage ImageStore;
     private File f;
     public ReadWriteTest()
          ErrorString = "";
          SuccessStatus = true;                    // Default set Success
          String filename = "MyPic.tif";
          ImageStore = null;
          if( filename == null )
               ErrorString = "No FileName";
               SuccessStatus = false;
               return;
          f = new File( filename );
          if(!readInFile( f ))
               return;
          String[] Names = ImageIO.getWriterFormatNames();
          System.out.println("Image Types Write Test" );
          for( int i = 0 ; i < Names.length ; i++ )
               System.out.println("Type: " + Names[i] +"    ");
               filename = "ImageDump/Test." + Names;
               System.out.println( filename );
               f = new File( filename );
               System.out.println("Attempting to Write Image Type: " + Names[i] );
               try
                    ImageIO.write(ImageStore, Names[i], f);
               catch( IOException IOE)
                    System.out.println("IO ERROR Writing Image : FAIL" );
     public static void main( String[] args )
          ReadWriteTest T = new ReadWriteTest();
     private boolean readInFile( File F )
          if( !F.exists() )
               ErrorString = "File Doesn't Exist";
               SuccessStatus = false;               
               return false;
          if( !F.canRead() )
               ErrorString = "Cannot Read() File";
               SuccessStatus = false;               
               return false;
               javax.imageio stuff
     //     ImageIO.scanForPlugins();
          try
               System.out.println("Attempting to decode Image");
               ImageStore = ImageIO.read( F );               //Magically create Buffered Image from supported 'Readers'
          catch( IOException IOE )
               ErrorString = "IO Error Decoding Image";
               SuccessStatus = false;
               return false;
          catch( IllegalArgumentException IAE )
               ErrorString = "Failure By Installed Reader: " + IAE.getMessage();
               SuccessStatus = false;
               return false;
          if( ImageStore == null )
               ErrorString = "Could Not Decode Image";
               SuccessStatus = false;
               return false;
          return true;