/**
  This class contains two helper functions, for reading and writing images.
 */

import java.awt.*;
import java.io.*;
import java.awt.image.*;

class ImageReaderWriter {

  /**
    Read an image from an InputStream.
    @param theComponent - images are device dependent so we need to have
          the component to generate the initial blank image.
    @param in - the input stream.
    @return the loaded image.
   */
  static Image readImage(Component theComponent, ObjectInputStream in) 
       throws IOException, ClassNotFoundException
  {
    int w = in.readInt();
    int h = in.readInt();
    int[] pixels = (int[])in.readObject();

    Image img=theComponent.createImage(new MemoryImageSource(w,h,pixels,0,w));

    // Now we need to wait until the image is fully produced

    // the MediaTracker constructor wants an ImageObserver
    // all components implement ImageObserver so use theComponent
    MediaTracker tracker = new MediaTracker(theComponent);

    // you can call addImage more times to track several images
    // with this one MediaTracker
    tracker.addImage(img, 0/*user selected id to identify the image*/);

    // you can also use waitForId(idNum) to wait for a specific image
    // this idNum is the same one passed in the addImage() call
    try { tracker.waitForAll(); }
    catch (InterruptedException e) {}

    return img;
  } 

  /**
    Write an image to an OutputStream.
    @param img - the Image to be written.
    @param out - the output stream.
   */
  static void writeImage(BufferedImage img, ObjectOutputStream out)
       throws IOException
  {
    int w = img.getWidth(null);
    int h = img.getHeight(null);
    int[] pixels = new int[w * h];
    PixelGrabber pg = new PixelGrabber(img, 0, 0, w, h, pixels, 0, w);
    try {
      pg.grabPixels();
    } catch (InterruptedException e) {
      System.err.println("interrupted waiting for pixels!");
      return;
    }
    if ((pg.getStatus() & ImageObserver.ABORT) != 0) {
      System.err.println("image fetch aborted or errored");
      return;
    }
    out.writeInt(w);
    out.writeInt(h);
    out.writeObject(pixels);
  }
}