VizHashPanel.java

/* Copyright 2011-2013 Edouard Garnier de Labareyre
 *
 * This file is part of ViszHash4j
 * Visual Hash implementation in java
 * This is free software under the zlib/libpng licence
 * http://www.opensource.org/licenses/zlib-license.php
 *
 * Widely inspired from VizHash_GD php code (https://github.com/sebsauvage/VizHash)
 * Thanks to Sebastien Sauvage for this piece of code
 */

import java.awt.Color;
import java.awt.Dimension;
import java.awt.GradientPaint;
import java.awt.Graphics;
import java.awt.Graphics2D;
import java.awt.RenderingHints;
import java.security.MessageDigest;
import java.util.ArrayList;
import javax.swing.JPanel;

/**
 * JPanel that computes and display the VizHash picture for a given message String
 * The obtained picture aims to be similar to those generated by VizHash_GD (https://github.com/sebsauvage/VizHash)
 */
public class VizHashPanel extends JPanel{

  
    private String message_hash="";
    
    private ArrayList<Integer>  values = new ArrayList<Integer>();
    private int values_index=0;
    
    private int width,height;
    
    public VizHashPanel(){
    }

    /**
     * Display the VizHash shape of a given message
     * @param message the message to vizhash
     * @return false if a problem is encoutered during computation
     */
    public boolean setValue(String message){
        try{
            //compute hash String
            String md5_hash = convertToHex(MessageDigest.getInstance("MD5").digest(message.getBytes("UTF8")));
            String sha1_hash = convertToHex(MessageDigest.getInstance("SHA1").digest(message.getBytes("UTF8")));
            message_hash=sha1_hash+md5_hash+new StringBuffer(sha1_hash+md5_hash).reverse().toString();

            //build int values array
            values = new ArrayList<Integer>();
            values_index=0;
            for(int i=0; i<message_hash.length();i+=2){
                int dec = Integer.parseInt(message_hash.substring(i,i+2),16);
                values.add(dec);
            }

            //paint component with this new value
            repaint();
        }catch(Exception e){
            System.out.println("Error while hashing string \""+message+"\":");
            e.printStackTrace();
            return false;
        }
        return true;
        
    }

    @Override
    public Dimension getPreferredSize() {
        return new Dimension(256,256);
    }

    @Override
    public void paintComponent(Graphics g) {
        
        values_index=0;
        width=this.getWidth();
        height=this.getHeight();
        
        Graphics2D g2 = (Graphics2D)g;
        RenderingHints rh = new RenderingHints(
        RenderingHints.KEY_ANTIALIASING,RenderingHints.VALUE_ANTIALIAS_ON);
        g2.setRenderingHints(rh);
        super.paintComponent(g);

        int red0 = getInt();
        int green0 = getInt();
        int blue0 = getInt();

        int red=red0;
        int green=green0;
        int blue=blue0;
        
        Color bg0 = new Color(red0,green0,blue0);

        //paint horizontal or vertical gradient in background
        GradientPaint bg = new GradientPaint(0,0,bg0,0, height,Color.BLACK);
        if(getInt()%2==0){
            bg = new GradientPaint(0,0,bg0,width,0,Color.BLACK);
        }
        g2.setPaint(bg);
        g2.fillRect(0, 0, width,height);

        //draw 7 or less shapes, in a similar color theme than background
        int action;
        Color color;
        for(int i=0;i<7;i++){
            action = getInt();
            color = new Color(red,green,blue);
            red=(red0+getInt()/25)%256;
            green=(green0+getInt()/25)%256;
            blue=(blue0+getInt()/25)%256;
            red0=red;
            green0=green;
            blue0=blue;
            drawShape(g,action,color);
        }
        //draw the last shape with a color than can be new
        color = new Color(getInt(),getInt(),getInt());
        drawShape(g,getInt(),color);             
    }

    /**
     * This function paints a filled shape which can be a rectangle, an ellipse, a polygon or an arc
     * @param g the graphic where to paint
     * @param action an integer between 0 and 255
     * @param color the color of the shape to paint
     */
    public void drawShape(Graphics g,int action,Color color){

        int w,h;
        
        g.setColor(color);

        switch(action%7){
            case 0:
                //rectangle
                int[] r = {getXCoordinate(),getYCoordinate(),getXCoordinate(),getYCoordinate()};//order of call of getInt() is important to stay the same as VizHash_GD
                int x0=Math.min(r[0],r[2]);
                int y0=Math.min(r[1],r[3]);
                int x1=Math.max(r[0],r[2]);
                int y1=Math.max(r[1],r[3]);
                g.fillRect(x0,y0,x1-x0,y1-y0);
                break;
            case 1:
            case 2:
                //ellipse
                int xc=getXCoordinate();
                int yc=getYCoordinate();
                w=getXCoordinate();
                h=getYCoordinate();
                g.fillOval(xc-(w/2),yc-(h/2),w,h);
                break;
            case 3:
                //polygon
                int[] p = {getXCoordinate(),getYCoordinate(),
                           getXCoordinate(),getYCoordinate(),
                           getXCoordinate(),getYCoordinate(),
                           getXCoordinate(),getYCoordinate()};
                int[] xPoints={p[0],p[2],p[4],p[6]};
                int[] yPoints={p[1],p[3],p[5],p[7]};
                g.fillPolygon(xPoints, yPoints, 4);
                break;
            case 4:
            case 5:
            case 6:
                //arc
                int as=getInt()*360/256;
                int ae=as+((getInt()*180)/256);
                int start=-as;
                int angle=as-ae;
                int cx=getXCoordinate();
                int cy=getYCoordinate();
                w=getXCoordinate();
                h=getYCoordinate();
                g.fillArc(cx-(w/2), cy-(h/2), w, h, start, angle);
                break;
        }
    }

    /**
     * This function returns the next int from the values array
     * @return an int from the values array
     */
    private int getInt(){
        int v = values.get(values_index);
        values_index++;
        values_index%=values.size();
        return v;
    }

    /**
     * Same as getInt but normalized to component width
     * @return int
     */
    private int getXCoordinate(){
        return width*getInt()/256;
    }

    /**
     * Same as getInt but normalized to component height
     * @return int
     */
    private int getYCoordinate(){ 
        return height*getInt()/256;
    }

     /**
     * This function converts the byte array in hexadecimal String
     * (snippet found on pastebin http://pastebin.com/air8WKN5)
     * @param data the byte array to convert
     * @return 
     */
    private static String convertToHex(byte[] data) {
        StringBuilder buf = new StringBuilder();
        for (int i = 0; i < data.length; i++) {
            int halfbyte = (data[i] >>> 4) & 0x0F;
            int two_halfs = 0;
            do {
                if ((0 <= halfbyte) && (halfbyte <= 9))
                    buf.append((char) ('0' + halfbyte));
                else
                    buf.append((char) ('a' + (halfbyte - 10)));
                halfbyte = data[i] & 0x0F;
            } while(two_halfs++ < 1);
        }
        return buf.toString();
    } 
}