source: tags/gsdl-2_70u-distribution/gsdl/src/java/org/nzdl/gsdl/GsdlCollageApplet/DisplayImages.java@ 11745

package org.nzdl.gsdl.GsdlCollageApplet;

import java.applet.*;
import java.awt.*;
import java.awt.image.*;
import java.awt.geom.*;
import java.util.*;

/** 
 *  @author Katrina Edgar
 *  @author David Bainbridge
 *
 *  Retrieves images from the download thread, determines an appropriate position
 *  for thes  images onscreen ensuring maximum whitespace coverage and minimal overlap
 *  when possible. Draws images using advanced image processing techniques when applicable,
 *  such as fading the edges of an image and discolouring backgrounds. Also re-uses images
 *  from those that have previously been displayed, or are aging onscreen, in order to
 *  to create movement when no new images have been downloaded. */
public class DisplayImages extends Thread {


    /** Will fire a removal operation when 4 images in the collage overlap a single area */
    static final int NO_IMAGES_OF_OVERLAP = 4;
    
    /** To determine if there are several images overlapped, can remove the
     *  layers underneath to save time in repainting */
    boolean overlap = false;

    /** Refers to download thread */
    DownloadImages download_images_ = null;

    /** Refers to applet */
    GsdlCollageApplet app_ = null;

    /** Applets width on screen */
    public static int app_x_dim_  = 0;

    /** Applets height on screen */
    public static int app_y_dim_  = 0;
    
    /** Background colour of the applet screen */
    protected Color bgcolor_        = null;

    /** Indicates whether java2 functionality should be used <br>
     *  If true will allow advanced image processing techniques to occur, 
     *  such as fading and colouring using pixel manipulation <br>
     *  If false, images will maintain an alpha value of 1 (appear solid), 
     *  newer images will simply be pasted on top of existing images <br> */
    protected boolean is_java2_     = false;

  
    /** Holds images currently on display in the applet */
    protected Vector inuse_    = null;
    
     /** Holds images ready to be used */
    protected Vector inuse_ready_    = null;

    /** Holds previously displayed images for re-use */
    protected Vector notinuse_ = null;
   
    protected Image    screen_buffer_    = null;
    protected Graphics screen_graphic_   = null;
    protected Image    finished_buffer_  = null;
    protected Graphics finished_graphic_ = null;
 
    Thread next_frame_ ;

    String dots[] = new String[]{" ",".","..","...","....",".....","......"};
    int dots_nums=0;
    boolean start_paint = false;
    /** Used to determine where to place new images on the applet to optimize
     *  whitespace coverage <br>
     *  A co-ordinate in the applet has a value of zero if it is whitespace,
     *  one if it is covered by one image, two if it is covered by two images,
     *  and so on. New images will be placed such that they cover the largest
     *  area of whitespace (zero valued co-ordinates) */
    public static int [] [] used_space = null;
    
  
    /**
     *  Starts the display images thread. Initialises variables using parameters and
     *  static values. Creates the blank applet screen, initialises the used space
     *  2D array to indicate that there are no images onscreen
     *
     *  @param app the applet to display the images on
     *  @param download_images thread from which to retrieve downloaded images
     *  @param is_java2 whether advanced image processing techniques should be used
     *  @param bgcolor the background colour of the applet screen */
    public DisplayImages(GsdlCollageApplet app, DownloadImages download_images,
             boolean is_java2, Color bgcolor)
    {
    super("DisplayImages");

    // parameters saved locally
    app_             = app;
    is_java2_        = is_java2;
    bgcolor_         = bgcolor;

    inuse_    = new Vector();
        notinuse_ = new Vector();
        inuse_ready_ = new Vector();
    download_images_ = download_images;
    // sets width and height
    if (is_java2_)
    {
        app_x_dim_  = app_.getWidth();
        app_y_dim_  = app_.getHeight();
    }
    else
    {
        app_x_dim_  = 645;
        app_y_dim_  = 780;
    }

    // creates initial screen
    screen_buffer_ = app_.createImage(app_x_dim_, app_y_dim_); 
    screen_graphic_ = screen_buffer_.getGraphics();
    screen_graphic_.setColor(bgcolor_);
    screen_graphic_.fillRect(0,0,app_x_dim_,app_y_dim_);
    
    finished_buffer_  = app_.createImage(app_x_dim_, app_y_dim_);
    finished_graphic_ = finished_buffer_.getGraphics();
    
    // initialises used space array to indicate an empty screen
    used_space = new int [app_x_dim_][app_y_dim_];  
    for (int n=0; n < app_x_dim_; n++)
        for (int m=0; m < app_y_dim_; m++)
        used_space[n][m] = 0;

        next_frame_ =  new Thread(new Runnable(){
                public void run() {
          
            Thread curr_thread = Thread.currentThread();
            
            while (curr_thread == next_frame_) {
            try {       
                Runtime rt = Runtime.getRuntime();
                //System.out.println("total: "+rt.totalMemory());
                //System.out.println("free:  "+rt.freeMemory());
                rt.gc();             
                        //System.out.println("**************next frame...");
                next_frame();
                Thread.sleep(app_. refreshDelay_);
               
                curr_thread = Thread.currentThread();
            } catch (Exception e) {
                            e.printStackTrace(); 
                break;
            }
            }
                    
           
        }


        });

     next_frame_.start();


    }

    /** Determines what the user has clicked on in the applet, either an image or whitespace
     *  @param x the x co-ordinate of the mouse
     *  @param y the y co-ordinate of the mouse
     *  @return the image that the user has clicked on or null if the user has clicked whitespace */
   public CollageImage clickedOnImage(int x, int y)
    {
    if (app_.verbosity() > 1)
    {
        System.err.print("Checking for clicked on image: ("+x+","+y+")");
    }

    
    // checks from last image down, as last images place will be at the top of the collage
    for (int i= inuse_.size() - 1; i >= 0; i--)
    {
        CollageImage collage_image = (CollageImage)inuse_.elementAt(i);
        if (collage_image.inside(x,y))
        {
        return collage_image;
        }
    }
    // no image at these co-ordinates, just whitespace
    return null;
    }

    /** Generates the images onscreen.
     *  Loops through the vector of currently displayed images and draws each one in turn.
     *  If the image is being drawn for the first time, its position will be determined
     *  and its alpha channel set as solid prior to drawing. <br>
     *  Drawing of the image will depend on whether or not java2 is enabled. If so then
     *  the image will be processed so that fading occurs with age, so that the edges 
     *  fade faster than the rest of the image and so that white images are slightly 
     *  discoloured to allow distinction. If java2 is not enabled, new images will simply
     *  be pasted on top of existing images without any special effects occuring<br>
     *  This function also deletes old images. If java2 is enabled then images are deleted
     *  once they have faded to a suitably low alpha value. If java2 is not enabled then
     *  images will be removed once there are greater than 25 images onscreen, to ensure
     *  the applet cannot be overloaded. */
    public  void display_collage() 
    {
    
    // if there is nothing new to add
    if (inuse_.size()==0) return;
    
    // otherwise need to re-generate images
    if (app_.verbosity() >= 2)
        {
        //system.err.println("Regenerating images");
        }
    
    // get each image currently onscreen inturn
    for (int i=0; i<inuse_.size();)
        {
        CollageImage collage_image = (CollageImage)inuse_.elementAt(i);
  
                if (!collage_image.isValid()){
            continue;
        }       

                int[] pixels = null;
        // the first time the image is painted, determine its position and size
        if (collage_image.fresh == true)
            {
            collage_image.process();
            }
        
        // advanced image processing may be used
        if (is_java2_)
            {
            // conducts fading and colouring of image
            pixels = collage_image.handlepixels(inuse_.size()-i); 
            }
        
        if (collage_image.fresh) {
            collage_image.fresh = false;
        }
        
        
        // if we remove when images have faded too much
        if (is_java2_) {
            if (collage_image.checkFaded(pixels)|| overlap)
            {
                overlap = false;
                
                CollageImage removed_image = (CollageImage)inuse_.elementAt(i);
                //System.out.println(removed_image.name_ + "is removed");
                inuse_.remove(i);
                // indicates space for this image is no longer used
                for (int n = removed_image.xl_; n < (removed_image.xl_ + removed_image.image_x_dim_); n++)
                for (int m = removed_image.yt_; m < (removed_image.yt_ + removed_image.image_y_dim_); m++)
                    if(used_space[n][m] != 0) {
                    used_space[n][m]--;
                    if (used_space[n][m] > NO_IMAGES_OF_OVERLAP)
                        overlap = true;
                    }
                
                // sets the image as fresh and adds it to the vector of images previously seen
                removed_image.fresh = true;
                notinuse_.addElement(removed_image);
            }
            else{
            i++;
            }
        }
        else 
            if (inuse_.size() > 25 || overlap) {
            overlap = false;
            
            CollageImage removed_image = (CollageImage)inuse_.elementAt(i);
            inuse_.remove(i);
            
            // indicates space for this image is no longer used
            for (int n = removed_image.xl_; n < (removed_image.xl_ + removed_image.image_x_dim_); n++)
                for (int m = removed_image.yt_; m < (removed_image.yt_ + removed_image.image_y_dim_); m++)
                if(used_space[n][m] != 0) {
                    used_space[n][m]--;
                if (used_space[n][m] > NO_IMAGES_OF_OVERLAP)
                    overlap = true;
                }
            
            // sets the image as fresh and adds it to the vector of images previously seen
            removed_image.fresh = true;
            notinuse_.addElement(removed_image);
            }
            else{
            i++;
            }    
        
        }
    }
    
  
    /** Alters the images currently on display in the applet <br>
     *  Changes are prioritised in the following way:
     *  1. If there are images that have been downloaded and are yet to be displayed 
     *  they will be added to the list of images in use. <br>
     *  2. Otherwise if there are images that have previously been displayed but
     *  are not currently on the applet screen, re-use one of these images. <br>
     *  3. Otherwise if there are any images on screen at all, take the oldest and
     *  repaint it as the newest. <br>
     *  Then the collage is asked to display and repaint with the new image set. */

     public  void next_frame()
    {
    double random = Math.random();
    
     
     if (inuse_ready_.size() > 0){
        int pos = (int) ((inuse_ready_.size() - 1) * random);
        CollageImage collage_image = (CollageImage) inuse_ready_.remove(pos);
        inuse_.addElement(collage_image);
    }
    else if (notinuse_.size()>0)
        {
            int position = (int) ((notinuse_.size() - 1) * random);
            
            CollageImage collage_image = (CollageImage)notinuse_.elementAt(position);
            notinuse_.remove(position);
            inuse_.addElement(collage_image);
            
            if (app_.verbosity()>3)
            {
            System.err.println("Re-using an image not on screen");
            }
        }
        else{
        if (app_.verbosity()>=4)
            System.err.println("No images in download area");
        }

    display_collage();
    
    }
  
  

    /** Paints the applet on the screen */
    public void paint(Graphics g)
    {

    screen_graphic_.setColor(bgcolor_);
    screen_graphic_.fillRect(0,0,app_x_dim_,app_y_dim_);

    // get each image currently onscreen inturn
    
    for (int i=0; i < inuse_.size(); i++)
        {
          
            CollageImage collage_image =null;
           try{
           collage_image = (CollageImage)inuse_.elementAt(i);
           start_paint = true;
        }
            catch(Exception e){
          System.out.println("exception in paint");                 
              break;
         }
       // don't paint new images yet
        if (collage_image.fresh) {
          if (app_.verbosity()>=1) {
            System.err.println("doing nothing...  "+ collage_image.name_ +" is fresh.");
           }
        }

        // advanced image processing may be used
        else if (is_java2_) {
          
            //the alphacomposite controls the blending of these two images.
            Graphics2D sg2d = (Graphics2D)screen_graphic_;
            sg2d.setComposite(AlphaComposite.getInstance(AlphaComposite.SRC_OVER));
            sg2d.setRenderingHint(RenderingHints.KEY_ANTIALIASING, 
                          RenderingHints.VALUE_ANTIALIAS_ON); 
            collage_image.expand();
            sg2d.drawImage(collage_image.image_, collage_image.af_, app_);
           }
        // simple image collage
        else
            {           // add the image to the collage
            
            screen_graphic_.drawImage(collage_image.image_, 
                          collage_image.xl_, collage_image.yt_,
                          collage_image.xr_, collage_image.yb_,
                          0,0,collage_image.image_x_dim_-1,
                          collage_image.image_y_dim_-1,  app_);
            }
    
        }
    
        
    finished_graphic_.drawImage(screen_buffer_,0,0,app_);
    

    if (finished_buffer_ != null)
        {
        g.drawImage(finished_buffer_, 0, 0, app_);
        if (!start_paint){
            g.setColor(Color.white);
            g.setFont(new Font("font",Font.PLAIN+Font.BOLD,30));
            g.drawString("Downloading" + dots[(dots_nums++)%dots.length],app_x_dim_/3-20,app_y_dim_/2-2);
        }
        }
    

    }

    /** Runs display thread by repeatedly calling the next frame,
     *  waiting for a specified delay period between calls */
    public void run() {
    try {
        
        Thread curr_thread = Thread.currentThread();
        
        while (curr_thread == this) {
        if (inuse_ready_.size() >= 1){
            Thread.sleep(1000);         
            continue;
        }    
        CollageImage collage_image = download_images_.getCollageImage();
    
        if (collage_image !=null){
            inuse_ready_.addElement(collage_image); 
        }
        curr_thread = Thread.currentThread();
        }
            
    } catch (Exception e) {
       e.printStackTrace();
           System.out.println("Display images thread is interrupted");
    }

    System.out.println("Display images thread stoped");
          
    }

}