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

#define WINDSIZEX 100
#define WINDSIZEY 100

#define X1   5.5
#define Y1   6.5
#define X2  10.5
#define Y2  12.5

void init(void)
{
   GLfloat fragColor[] = {0.8, 0.5, 0.2, 1.0};
   GLfloat fogColor[] = {0.1, 0.1, 0.8, 1.0};

   glDisable (GL_DITHER);

   glEnable(GL_FOG);
   glFogfv (GL_FOG_COLOR,      fogColor);
   glFogf  (GL_FOG_START,      0.1);
   glFogf  (GL_FOG_END,       0.9);
   glFogf  (GL_FOG_COORDINATE_SOURCE, GL_FOG_COORDINATE);

   glColor4fv(fragColor);
   glFogf(GL_FOG_MODE, GL_LINEAR);

}

static void test(void)
{    
   GLfloat buf[3];
   GLubyte bitmap[] = {0xFF};

   glClear (GL_COLOR_BUFFER_BIT);

   glFogCoordf(0.2);
   glRasterPos2f (X1, Y1);
   glBitmap (1, 1, 0.0, 0.0, 0.0, 0.0, bitmap);

   glFogCoordf(0.8);
   glRasterPos2f (X2, Y2);
   glBitmap (1, 1, 0.0, 0.0, 0.0, 0.0, bitmap);

   glReadPixels(X1, Y1, 1, 1, GL_RGB, GL_FLOAT, buf);
   printf("pixel: %f %f %f\n", buf[0], buf[1], buf[2]);

   glReadPixels(X2, Y2, 1, 1, GL_RGB, GL_FLOAT, buf);
   printf("pixel: %f %f %f\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; 
}