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

#define WINDSIZEX 100
#define WINDSIZEY 100

#define TEX_SIZE            64

GLfloat colorTable[][3] = {
   {
      0.0, 0.0, 0.0
   },
   {
      1.0, 0.0, 0.0
   },
   {
      0.0, 1.0, 0.0
   },
   {
      0.0, 0.0, 1.0
   },
   {
      1.0, 1.0, 1.0
   },
   {
      1.0, 1.0, 0.0
   },
   {
      1.0, 0.0, 1.0
   },
   {
      0.0, 1.0, 1.0
   }
};


void CreateTexture(GLint texEnum, GLfloat *buf)
{
   GLfloat *ptr;
   GLint level, size, i, area;

   level = 0;
   for (size = TEX_SIZE; size > 0; size /= 2)
   {
      area = size;

      ptr = buf;
      for (i = 0; i < area; i++)
      {
	 *ptr++ = colorTable[level][0];
	 *ptr++ = colorTable[level][1];
	 *ptr++ = colorTable[level][2];
      }

      glTexImage1D(GL_TEXTURE_1D, level, 3, size, 0, GL_RGB,
	    GL_FLOAT, (unsigned char *)buf);

      level++;
   }
}


GLuint   texName[1];

GLfloat *buf;

void init(void)
{
   glGenTextures(1, texName);

   glDisable(GL_DITHER);
   glClearColor(0.0, 0.0, 0.0, 1.0);

   buf = (GLfloat *)malloc(WINDSIZEX*WINDSIZEY*3*sizeof(GLfloat));

   glBindTexture(GL_TEXTURE_1D, texName[0]);
   CreateTexture(GL_TEXTURE_1D, buf);
}

void draw()
{
   GLint   size;
   GLfloat s, t;

   s = 1; t = 0;

   size = TEX_SIZE;
      glBegin(GL_POLYGON);
      glTexCoord2f(0.0, 0.0);

      glVertex2i(0, 0);

      glTexCoord2f(0.0, t);
      glVertex2i(0, size);
      glTexCoord2f(s, t);
      glVertex2i(size, size);

      glTexCoord2f(s, 0.0);
      glVertex2i(size, 0);
      glEnd();

      glReadPixels(0, 0, size, size, GL_RGB, GL_FLOAT, buf);
      printf("get pixel at (0, 0): %f %f %f\n", buf[0], buf[1], buf[2]);
      // printf("should be: %f %f %f %f\n", expected[0], expected[1], expected[2], expected[3]);
}

void test(void)
{    

   glClear(GL_COLOR_BUFFER_BIT);

   glActiveTextureARB(GL_TEXTURE0_ARB);
   glBindTexture(GL_TEXTURE_1D, texName[0]);

   glTexParameteri(GL_TEXTURE_1D, GL_TEXTURE_LOD_BIAS_EXT, 1);

   glTexParameteri(GL_TEXTURE_1D, GL_TEXTURE_MAG_FILTER, GL_LINEAR); 
   glTexParameteri(GL_TEXTURE_1D, GL_TEXTURE_MIN_FILTER, GL_NEAREST_MIPMAP_LINEAR); 

      glTexEnvi(GL_TEXTURE_FILTER_CONTROL_EXT, GL_TEXTURE_LOD_BIAS_EXT, 1);

      glEnable(GL_TEXTURE_1D);
      glTexEnvi(GL_TEXTURE_ENV, GL_TEXTURE_ENV_MODE, GL_DECAL);

      draw();
      glDisable(GL_TEXTURE_1D);
}


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; 
}