#include <GL/glut.h>
#include <stdlib.h>
#include <stdio.h>
#include <math.h>

#define WINDSIZEX 100
#define WINDSIZEY 100


void init(void)
{
}

static void test(void)
{    
   GLfloat *pixels;
   int i;
   GLubyte bitmap[8*8];

   pixels = (GLfloat *) malloc(WINDSIZEX*WINDSIZEY*sizeof(GLfloat));

   for(i = 0; i < 8*8; i++){
      bitmap[i]=0xFF;
   }

   /*
      glDrawBuffer(GL_FRONT_LEFT);
      glClear(GL_COLOR_BUFFER_BIT);
      glDrawBuffer(GL_BACK_LEFT);
      glClear(GL_COLOR_BUFFER_BIT);
    */

   glDrawBuffer(GL_LEFT);

   glClearColor(1.0,0.0,0.0,0.0);
   glClear(GL_COLOR_BUFFER_BIT);

   glColor4f(0.0, 1.0, 0.0, 0.0);

   glRasterPos2f(3 + 0.25, 6 + 0.25);
   glBitmap (8, 8, 0.0, 0.0, 0.0, 0.0, bitmap);


   glReadBuffer(GL_FRONT_LEFT);
   glReadPixels(0, 0, WINDSIZEX, WINDSIZEY, GL_GREEN, GL_FLOAT, pixels);

   int colored = 0;

   for(i = 0; i < WINDSIZEX *WINDSIZEY; i++)
      if(pixels[i] == 1.0) colored++;

   printf("colored pixel : %d\n", colored);
}

void display(void)
{
   glViewport(0, 0, WINDSIZEX, WINDSIZEY);
   glMatrixMode(GL_PROJECTION);
   glLoadIdentity();
   gluOrtho2D(0, WINDSIZEX, 0, WINDSIZEY);
   glMatrixMode(GL_MODELVIEW);
   glLoadIdentity();

   test();
}

int main(int argc, char** argv)
{
   glutInit(&argc, argv);
   glutInitDisplayMode(GLUT_DOUBLE | GLUT_RGB);
   glutInitWindowSize(WINDSIZEX, WINDSIZEY);
   glutInitWindowPosition(100, 100);
   glutCreateWindow(argv[0]);
   init();
   glutDisplayFunc(display);
   glutMainLoop();
   return 0; 
}