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

#define WINDSIZEX 100
#define WINDSIZEY 100


void
init (void)
{
    int i;
    GLfloat white[] = { 1.0, 1.0, 1.0, 1.0 };

    glClearColor (0.0, 0.0, 0.0, 1.0);
    glColor4fv (white);
    glDisable (GL_DITHER);
}

#define SIZE 8
static void
test (void)
{
    GLubyte t[SIZE * SIZE * 4];
    int i, j;
    GLfloat buf[3];
    GLubyte bitmap[1] = {0xAA};

    glClearColor (0.0, 0.0, 0.0, 1.0);
    glClear (GL_COLOR_BUFFER_BIT);

    for (i=0; i<SIZE; i++)
        for (j=0; j<SIZE; j++)
        {
            t[4*(i*SIZE+j)] = i % 256;
            t[4*(i*SIZE+j)+1] = i % 256;
            t[4*(i*SIZE+j)+2] = i % 256;
            t[4*(i*SIZE+j)+3] = 0;
        }


    glRasterPos2f (0.0, 0.0);
    glDrawPixels (SIZE, SIZE, GL_BGRA, GL_UNSIGNED_BYTE, t);
    glReadPixels (0, 0, 1, 1, GL_RGB, GL_FLOAT, buf);
    printf ("after drawpixel, read out pixels: (0, 0) = (%f, %f, %f)\n", buf[0], buf[1],
            buf[2]);


    glClear (GL_COLOR_BUFFER_BIT);
    glColor3f (1.0, 1.0, 1.0);
    glRasterPos2f(0.0, 0.0);
    glBitmap(8, 1, 0, 0, 0, 0, bitmap);
    glReadPixels (0, 0, 1, 1, GL_RGB, GL_FLOAT, buf);
    printf ("after glBitmap, read out pixels: (0, 0) = (%f, %f, %f), ", buf[0], buf[1],
            buf[2]);
    printf ("should be (%f, %f, %f)\n", 1.0, 1.0, 1.0);
}

void
display (void)
{
    glMatrixMode (GL_PROJECTION);
    glLoadIdentity ();
    glOrtho (0, WINDSIZEX, 0, WINDSIZEY, 0, -1.0);
    test ();
}

int
main (int argc, char **argv)
{
    glutInit (&argc, argv);
    glutInitDisplayMode (GLUT_SINGLE | GLUT_RGBA);
    glutInitWindowSize (WINDSIZEX, WINDSIZEY);
    glutInitWindowPosition (100, 100);
    glutCreateWindow (argv[0]);
    init ();
    glutDisplayFunc (display);
    glutMainLoop ();
    return 0;
}