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

#define WINDSIZEX 100
#define WINDSIZEY 100

#define TEXSIZE 64


static GLfloat *buf1;               // Buffers for reading screen

static GLfloat *rgbFourTexture;

static GLuint  texImages;

static GLfloat mMap[] = {
   1.0, 0.0, 0.0, 0.0,
   0.0, 1.0, 0.0, 0.0,
   1.0, 1.0, 0.0, 0.0,
   0.0, 0.0, 0.0, 1.0,
};

static GLfloat mScale[] = {
   1.0/64.0,      0.0, 0.0, 0.0,
   0.0,      1.0/64.0, 0.0, 0.0,
   0.0,           0.0, 0.0, 0.0,
   0.0,           0.0, 0.0, 1.0,
};

typedef struct {
   GLfloat s1;
   GLfloat t1;
   GLfloat s2;
   GLfloat t2;
   GLfloat r;
   GLfloat q;
} COORD_RECT;


static COORD_RECT pcrect = { -4.0, -4.0, 124.0, 124.0,  4.0,   2.0};

//static COORD_RECT pcrect = { 0.0, 0.0, 64.0, 64.0,  0, 0};

GLfloat colorMap[][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
   }
};


static void CreateFourColorTexture(void)
{
   GLint   x, y, colorIndex;
   GLint   xmappos, ymappos;
   GLfloat *prgb = rgbFourTexture;

   for (y = 0; y < TEXSIZE; y++) {
      for (x = 0; x < TEXSIZE; x++) {
	 xmappos = x / 4;
	 ymappos = y / 4;
	 colorIndex = (xmappos + ymappos + 1) % 4;
	 *prgb++ = colorMap[colorIndex][0];
	 *prgb++ = colorMap[colorIndex][1];
	 *prgb++ = colorMap[colorIndex][2];
      }
   }
}


void init()
{
   glDisable(GL_DITHER);

   glClearColor (0.0, 0.0, 0.0, 0.0);

   buf1 = (GLfloat *)malloc(WINDSIZEX*WINDSIZEY*sizeof(GLfloat)*3);
   rgbFourTexture   = (GLfloat *)malloc(TEXSIZE*TEXSIZE*3*sizeof(GLfloat));

   glGenTextures(1, &texImages);     

   glBindTexture (GL_TEXTURE_2D, texImages);

   glTexParameteri (GL_TEXTURE_2D, GL_TEXTURE_WRAP_S, GL_REPEAT);
   glTexParameteri (GL_TEXTURE_2D, GL_TEXTURE_WRAP_T, GL_REPEAT);
   glTexParameteri (GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_NEAREST);
   glTexParameteri (GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_NEAREST);

   CreateFourColorTexture ();
   glTexImage2D (GL_TEXTURE_2D, 0, GL_RGB, TEXSIZE, TEXSIZE,
	 0, GL_RGB, GL_FLOAT, rgbFourTexture);
   glEnable (GL_TEXTURE_2D);

   glMatrixMode (GL_TEXTURE);
   glLoadIdentity ();
   glLoadMatrixf (mScale);
   glMultMatrixf (mMap);
}

#define X1   4
#define Y1   4
#define X2  68
#define Y2  68

long Test ()
{

   GLint   x;

   glReadPixels(X1, Y1, X2, Y2, GL_RGB, GL_FLOAT, buf1);
   for (x = 0; x < 64; x++)
	   printf("pixel color: %f %f %f\n", buf1[x*3], buf1[x*3+1], buf1[x*3+2]);
   return 0;
}


void test(){
   glClear (GL_COLOR_BUFFER_BIT);

   glBindTexture (GL_TEXTURE_2D, texImages);
   glBegin (GL_QUADS);
   glTexCoord4d (pcrect.s1, pcrect.t1, pcrect.r, pcrect.q);
   glVertex2f (X1, Y1);
   glTexCoord4d (pcrect.s2, pcrect.t1, pcrect.r, pcrect.q);
   glVertex2f (X2, Y1);
   glTexCoord4d (pcrect.s2, pcrect.t2, pcrect.r, pcrect.q);
   glVertex2f (X2, Y2);
   glTexCoord4d (pcrect.s1, pcrect.t2, pcrect.r, pcrect.q);
   glVertex2f (X1, Y2);
   glEnd ();

/*   glBegin (GL_QUADS);
   glTexCoord2d (pcrect.s1, pcrect.t1);
   glVertex2f (X1, Y1);
   glTexCoord2d (pcrect.s2, pcrect.t1);
   glVertex2f (X2, Y1);
   glTexCoord2d (pcrect.s2, pcrect.t2);
   glVertex2f (X2, Y2);
   glTexCoord2d (pcrect.s1, pcrect.t2);
   glVertex2f (X1, Y2);
   glEnd ();
*/
   Test();

//   exit(0);
}

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

   test();
}



void main(int argc, char** argv)
{
   glutInit(&argc, argv);
   glutInitDisplayMode (GLUT_SINGLE | GLUT_RGBA);
   glutInitWindowSize (WINDSIZEX, WINDSIZEY);
   glutInitWindowPosition (100, 100);
   glutCreateWindow ("hello");
   init();
   glutDisplayFunc(display);
   glutMainLoop();
}