Distance Transform of a Binary Image in JAVA - Working Source Code

[Kalyan]

The Distance Transform of a Binary Image

This is a image processing program which performs the distance transform of a binary image.Distance transform is widely used for image thinning and finding skeleton of an image.

//1:newfndistrans.java
//2:A bmp monochrome image(preferably 512-512)
//make the image from mspaint or any other source


import java.io.*;
import javax.swing.*;
import java.awt.*;
import java.awt.event.*;
public class newfndistrans extends JFrame{
   frame frm=null;
   File f;
   FileInputStream ff;
   Color cl;
    int count;
    int  a[];

    int rnum,gnum;
   int xsize;
   int ysize;
  final int sample=5;
  String str=null;

newfndistrans(String str)
{
    super(str);
    frm=new frame();


    count=0;
    a=new int[8];
    rnum=0;gnum=0;
}

    public void paint(Graphics g)
   {
      int x,y,i=0,j=0,temp;

          try{

      System.out.println("Starting");
      System.out.println("filename="+frm.getfilename());
      try{f=frm.getfilename();
            ff=new FileInputStream(f);
           }catch(Exception e){
              System.out.println("error in reading file");
              }
     ff.skip(18);
     i=ff.read();
     i=((ff.read()<<8 )|i );
     i=((ff.read()<<16 )|i );
     i=((ff.read()<<24 )|i );
     xsize=i;
     System.out.println("width="+xsize);
     i=0;
     i=ff.read();
     i=((ff.read()<<8 )|i );
     i=((ff.read()<<16 )|i );
     i=((ff.read()<<24 )|i );
     ysize=i;
     System.out.println("Height="+ysize);

     ff.skip(38);//62-(2+16+4+4=26)=36, actually total=62 Bytes header
     //note:make it 38 for nrectbit1.bmp and nrectbit2.bmp
     x=0;y=ysize;
     int pix[][],mat1[][];
     pix=new int[xsize][ysize];
     mat1=new int[xsize][ysize];
     System.out.println("here");
      while(true)
      {

         rnum=ff.read();
         //System.out.println("rnum="+rnum);
         if(rnum==-1)break;
         count=7;
   //image has 0 for black ,1 for white,but my convention is opposite
      while(rnum>0)
         {
            gnum=rnum%2;
            if(gnum==0)a[count]=1;
             else a[count]=0;
            count--;
            rnum=rnum/2;
         }
         while(count>=0)
         {a[count]=1;count--;
         }
         for(i=0;i<=7;i++)
         {if(a==0)cl=new Color(255,255,255);
            else cl=new Color(0,0,0);
           pix

• [y-1]=a;
             mat1
  • [y-1]=a;
                g.setColor(cl);
                g.drawRect(x,y,1,1);
                x++;
                if(x==xsize){x=0;y--;}
              }
             }//end while
    
    System.out.println("File read successfully");
    //sleep for 4 seconds(4000 msec)
    try{Thread.sleep(4000);
    }catch(Exception e){}
    //clear the region where the image was drawn,area near the boundaries
    are
    also cleaned
    for(j=0;j<=ysize+2;j++)
    for(i=0;i<=xsize+2;i++)
      g.clearRect(i,j,1,1);
    //cleaning done above
    
    //0 means white,1 means black
    //perform the distance transform
    for(j=0;j<ysize;j++)
    for(i=0;i<xsize;i++)
    {
      if(mat1[j]==0)continue;
      if((j==0)||(j==ysize-1)){mat1[j]=1;continue;}
       if((i==0)||(i==xsize-1)){mat1[j]=1;continue;}
    
    
    temp=findmin(mat1[i-1][j],mat1[i-1][j-1],mat1[j-1],mat1[i+1][j-1]);
          mat1[j]=temp+1;
    }
    
    
    
    //perform the distance transform from bottom
    for(j=ysize-1;j>=0;j--)
    for(i=xsize-1;i>=0;i--)
    {if(mat1[j]==0)continue;
      if((j==0)||(j==ysize-1)){mat1[j]=1;continue;}
      if((i==0)||(i==xsize-1)){mat1[j]=1;continue;}
    
    
    temp=findmin(mat1[i-1][j+1],mat1[j+1],mat1[i+1][j+1],mat1[i+1][j]);
          if(temp>(mat1[j]-1))temp=mat1[j]-1;
          mat1[j]=temp+1;
    }
    
    int max=-9999,colornum,i1,j1,globmax=-9999;
    x=0;y=0;
    for(j=0;j<ysize-(ysize%sample);j+=sample)
    for(i=0;i<xsize-(xsize%sample);i+=sample)
    {
       max=-9999;
       for(j1=j;j1<j+sample;j1++)
       for(i1=i;i1<i+sample;i1++)
       if(max<mat1[i1][j1])
       {
          max=mat1[i1][j1];
          //xcord=i1;ycord=j1;
       }
       //out of both above for loops
       if(globmax<max)globmax=max;
    
    
       if(max!=0)
       {
       System.out.println("max="+max);
       for(j1=j;j1<j+sample;j1++)
       for(i1=i;i1<i+sample;i1++)
          mat1[i1][j1]=max;
       }
    
    }
    System.out.println("globmax="+globmax);
    for(j=0;j<ysize;j++)
    for(i=0;i<xsize;i++)
      {colornum=(mat1[j]*255)/globmax;//contrast enhancement
       colornum=255-colornum;
       cl=new Color(colornum,colornum,colornum);
       g.setColor(cl);
       g.drawRect(i,j,1,1);
      }
    ff.close();
    System.out.println("program ends");
          }//end try block
       catch(Exception e)
          {System.out.println("Error"+e.getMessage());
          }
    
    
    
          }
    int findmin(int num1,int num2,int num3,int num4)
    {
       int min=4000;
       if(min>num1)min=num1;
       if(min>num2)min=num2;
       if(min>num3)min=num3;
       if(min>num4)min=num4;
       return(min);
    }
    
       public static void main(String args[])
       {
    
          JFrame frm=new newfndistrans("Distance Transform");
          frm.setSize(700,700);
          frm.setVisible(true);
    
    
       }//end main()
    
    }// end class fndistrans
    class frame extends JFrame{
       JButton but;
       JFileChooser fch;
        String filename;
        File file=null;
       //Container con;
       boolean temp;
       frame()
       { super("FileReading");
         setSize(700,500);
         setLayout(new FlowLayout());
    
         temp=true;
         but=new JButton("Open the binary file");
         add(but);
         fch=new JFileChooser();
         but.addMouseListener(new MouseAdapter()
         { public void mousePressed(MouseEvent me)
            {
               int retval=fch.showOpenDialog(but);
               if(retval==JFileChooser.APPROVE_OPTION)
               {
                  file=fch.getSelectedFile();
                  filename=file.getName();
                  System.out.println("1filename="+filename);
                  temp=false;
               }
    
            }
    
         });
         setVisible(true);
       while(temp);
       }//end constructor
    File getfilename()
    {System.out.println("filename="+filename);
       return file;
    }
    
    }