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

#define WINDSIZEX 100
#define WINDSIZEY 100


void init(void)
{
   glDisable(GL_DITHER);
}

static void test(void)
{    
   unsigned char buf[4];
   unsigned char destColor[] = { 34, 45, 56}, 
		 srcColor[] = {23, 34, 45};
   GLfloat x = 2, y = 2;
   GLubyte bitmap[] ={0xff, 0xff};

   glColor3ubv(destColor);
   glBegin(GL_POINTS);
   glVertex2f(x, y);
   glEnd();

   glEnable(GL_COLOR_LOGIC_OP);
   glLogicOp(GL_CLEAR); //AND);
   glColor3ubv(srcColor);
   glRasterPos2f(x, y);
   glBitmap(1, 1, 0, 0, 0, 0, bitmap);


   /* glBegin(GL_POINTS);
      glVertex2f(x, y);
      glEnd();
    */


   glReadPixels(x, y, 1, 1, GL_RGBA, GL_UNSIGNED_BYTE, buf);
   printf("draw pixel at (2, 2): %d %d %d\n", buf[0], buf[1], buf[2]);
}

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_SINGLE | GLUT_RGB);
   glutInitWindowSize(WINDSIZEX, WINDSIZEY);
   glutInitWindowPosition(100, 100);
   glutCreateWindow(argv[0]);
   init();
   glutDisplayFunc(display);
   glutMainLoop();
   return 0; 
}