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

#define WIN_WIDTH 128
#define WIN_HEIGHT 128
#define BITMAP_WIDTH 1
#define BITMAP_HEIGHT 1
#define ALIGN 1
GLfloat read_buf[4 * BITMAP_WIDTH * BITMAP_HEIGHT];
static GLfloat r_map[] = { 0, 1 };
static GLfloat g_map[] = { 0, 0 };
static GLfloat b_map[] = { 1, 0 };
static GLfloat a_map[] = { 1, 1 };
static GLubyte data[] = { 0x8f, 0xff, 0x7f, 0x70 };

static GLuint tex_name;

void init()
{
	int i, j;

	glMatrixMode(GL_PROJECTION);
	glLoadIdentity();
	glTranslatef(-1.0, -1.0, 0.0);
	glScalef(2.0/WIN_WIDTH, 2.0/WIN_HEIGHT, 1.0);

	glDisable(GL_DITHER);
	glClearColor(1, 1, 1, 1);
	glBlendFunc(GL_SRC_ALPHA, GL_ZERO);

	glPixelMapfv(GL_PIXEL_MAP_I_TO_R, 2, r_map);
	glPixelMapfv(GL_PIXEL_MAP_I_TO_G, 2, g_map);
	glPixelMapfv(GL_PIXEL_MAP_I_TO_B, 2, b_map);
	glPixelMapfv(GL_PIXEL_MAP_I_TO_A, 2, a_map);

	glPixelTransferi(GL_MAP_COLOR, GL_FALSE);

	glPixelStorei(GL_UNPACK_LSB_FIRST, GL_FALSE);
	glPixelStorei(GL_UNPACK_ROW_LENGTH, 0);
	glPixelStorei(GL_UNPACK_ALIGNMENT, ALIGN);

	glGenTextures(1, &tex_name);
	glBindTexture(GL_TEXTURE_2D, tex_name);

	glTexEnvi(GL_TEXTURE_ENV, GL_TEXTURE_ENV_MODE, GL_REPLACE);
	glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_NEAREST);
	glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_NEAREST);
}



void display()
{
	int i, j, k, pixel;
	GLubyte zero_data = 0;

	memset(read_buf, 0xff, sizeof(read_buf));	//reset

	for (k = 0; k < (sizeof(data)/sizeof(GLubyte)); k ++) {

	glClear(GL_COLOR_BUFFER_BIT);
	glNewList(1, GL_COMPILE_AND_EXECUTE);
		glEnable(GL_TEXTURE_2D);
		glBindTexture(GL_TEXTURE_2D, tex_name);

		glTexImage2D(GL_TEXTURE_2D, 0, GL_RGBA, 
			BITMAP_WIDTH, BITMAP_HEIGHT, 0,
			GL_COLOR_INDEX, GL_BITMAP, &data[k]);

		glBegin(GL_POLYGON);
		glTexCoord2f(0,0); glVertex2f(0, 0);
		glTexCoord2f(1,0); glVertex2f(BITMAP_WIDTH, 0);
		glTexCoord2f(1,1); glVertex2f(BITMAP_WIDTH, BITMAP_HEIGHT);
		glTexCoord2f(0,1); glVertex2f(0, BITMAP_HEIGHT);
		glEnd();
		glDisable(GL_TEXTURE_2D);
	glEndList();
	glFlush();

	glReadPixels(0, 0, BITMAP_WIDTH, BITMAP_HEIGHT, 
		GL_RGBA, GL_FLOAT, read_buf);

	printf("data[0x%x], ", data[k]);
	if (data[k] & 0x80) {
		printf("foreground: expected RGBA (%1.1f, %1.1f %1.1f %1.1f)\n",
			r_map[1], g_map[1], b_map[1], a_map[1]);
	} else {
		printf("background: expected RGBA (%1.1f, %1.1f %1.1f %1.1f)\n",
			r_map[0], g_map[0], b_map[0], a_map[0]);
	}

	printf("First execution, Readback RGBA:\n");
	for (i = 0; i < BITMAP_HEIGHT; i ++) {
		for (j = 0; j < BITMAP_WIDTH; j ++) {
			pixel = j + i*BITMAP_WIDTH;
			printf("pixel[%d, %d]: %1.1f %1.1f %1.1f %1.1f\n", j, i,
				read_buf[pixel*4], read_buf[pixel*4+1], 
				read_buf[pixel*4+2], read_buf[pixel*4+3]);
		}
	}

	/* 2nd time execution from call list */
	glCallList(1);
	glDeleteLists(1,1);

	memset(read_buf, 0xff, sizeof(read_buf));	//reset
	glReadPixels(0, 0, BITMAP_WIDTH, BITMAP_HEIGHT, 
		GL_RGBA, GL_FLOAT, read_buf);

	printf("CallList execution, Readback RGBA:\n");
	for (i = 0; i < BITMAP_HEIGHT; i ++) {
		for (j = 0; j < BITMAP_WIDTH; j ++) {
			pixel = j + i*BITMAP_WIDTH;
			printf("pixel[%d, %d]: %1.1f %1.1f %1.1f %1.1f\n", j, i,
				read_buf[pixel*4], read_buf[pixel*4+1], 
				read_buf[pixel*4+2], read_buf[pixel*4+3]);
		}
	}
	printf("------------------------------------\n");
	}	//end for(k)

}


int main(int argc, char**argv)
{
	glutInit(&argc, argv);
	glutInitDisplayMode (GLUT_SINGLE | GLUT_RGB);
	glutInitWindowSize (WIN_WIDTH, WIN_HEIGHT);
	glutInitWindowPosition (100, 100);
	glutCreateWindow ("hello");
	init();
	glutDisplayFunc(display);
	glutMainLoop();
}