1stprogram.cpp

#include <iostream>
#include <GL/glut.h>
using namespace std;

unsigned char get_col[50][50][3];
void init(void)
{
  glClearColor(1.0, 0.0, 0.0, 0.0);
 // glClear(GL_COLOR_BUFFER_BIT);
  glMatrixMode(GL_PROJECTION);
  glOrtho(0.0,100.0,0.0,100.0,0.0,100.0);
}
void readbuffervalue(GLint start, GLint end)
{
  for(int i=start; i<=end; i++){
    for(int j=start; j<=end; j++){
	glReadPixels(i, j, 1, 1, GL_RGB, GL_UNSIGNED_BYTE, get_col[i][j]);
}}}
bool checkcolor(GLint x, GLint y)
{
  int r = get_col[x][y][0];
  int g = get_col[x][y][1];
  int b = get_col[x][y][2];
  if((r!=255)&&(g==255)&&(b!=255))
  return true;
  else
  return false;
}
void putpoint(int x, int y)
{
  get_col[x][y][0] = 0;
  get_col[x][y][1] = 0;
  get_col[x][y][2] = 255;
  glColor3f(0.0,0.0,1.0);
  glPointSize(2);
  glBegin(GL_POINTS);
  glVertex2i(x,y);
  glEnd();
  glFlush();
}
void filling(int x, int y)
{
 bool value = checkcolor(x,y);
 if(value == true)
  {putpoint(x,y);
 
  filling(x+1,y);
  filling(x-1,y);
  filling(x,y+1);
  filling(x,y-1);
}}
void displayfunc()
{
  glClear(GL_COLOR_BUFFER_BIT);
  glColor3f(0.0,1.0,0.0);
  glRecti(0,0,50,50);
  glFlush();
  readbuffervalue(0,49);
  filling(40,40);
  glFlush();
}

 
int main(int argc, char **argv)
{
  glutInit(&argc, argv);
  glutInitDisplayMode(GLUT_SINGLE | GLUT_RGB);
  glutInitWindowSize(300,300);
  glutInitWindowPosition(100,100);
  glutCreateWindow("color-filling");
  init();
  glutDisplayFunc(displayfunc);
 glutMainLoop();
 return 0;
} 

2ndprogram.cpp

 #include <iostream>
    #include <GL/glut.h>

    using namespace std;
    unsigned char pick_col[50][50][3];
    void init(void)
    {
        glClearColor(1.0,0.0,0.0,0.0); 
        glMatrixMode(GL_PROJECTION);
        glOrtho(0.0,100.0,0.0,100.0,0.0,100.0);
    }

    void readAllToBuffer( GLint _start, GLint  _end ) 
    {

        for (int i=_start;i<_end;i++)
        {
            for (int j=_start;j<_end;j++)
            {
                glReadPixels(i , j , 1 , 1 , GL_RGB , GL_UNSIGNED_BYTE , pick_col[i][j]);
            }
        }
    }

    bool getpixelcolor(GLint x, GLint y)
    {
        int r,g,b;
        r = pick_col[x][y][0];
        g = pick_col[x][y][1];
        b = pick_col[x][y][2];

        //cout<<"b:"<<b<<"\r\n";
        if ((r!=255)&&(b!=255)&&(g==255))//g==1
        {
            return true;
        }
        else    
        {
            return false;
        }
    }

    void PutPoint( int x, int y ) 
    {
         pick_col[x][y][0]=0;
         pick_col[x][y][1]=0;
         pick_col[x][y][2]=255;
        glPointSize(2);
        glBegin (GL_POINTS);
        glColor3f (0.0,0.0,1.0);
        glVertex2i (x,y);
        glEnd();
       // glFlush();

    }

    void Filling(int x,int y)
    {
        bool Value=getpixelcolor(x,y);
        if (Value==true)
        {
            PutPoint(x, y);

            Filling (x+1,y);
            Filling (x-1,y);
            Filling (x,y+1);
            Filling (x,y-1);
        }
    }
    void displayfnc()
    {   glClear(GL_COLOR_BUFFER_BIT);

            glColor3f(0.0,1.0,0.0);
            glRecti(0,0,50,50);
            glFlush();
            readAllToBuffer(0, 49);
            Filling(40,40);
            glFlush();

    }
 /*   void Timer(int extra)
    {
        glutPostRedisplay();
        glutTimerFunc(30,Timer,0);
    }*/
    int  main(int argc, char** argv)
    {

        glutInit(&argc, argv);
        glutInitDisplayMode(GLUT_SINGLE | GLUT_RGB);
        glutInitWindowSize(300,300);
        glutInitWindowPosition(10, 10);
        glutCreateWindow("BoundaryFill");
        init();
        glutDisplayFunc(displayfnc);
        //glutTimerFunc(10,Timer,0);
        glutMainLoop();
        return 0;
    }