title: glDrawPixels: cannot see program output
body: <p>I am trying to follow the glDrawPixels example from Chapter 8 of the red book
  (which is incomplete) but cannot see anything (I just see a black screen with
  no pixmapwhen I run the code. Any ideas what I am doing wrong?</p>
  
  <pre><code>#include &lt;GL/glut.h&gt;
  
  #define CHECK_IMAGE_WIDTH 64
  #define CHECK_IMAGE_HEIGHT 64
  static GLubyte checkImage[CHECK_IMAGE_WIDTH][CHECK_IMAGE_HEIGHT][3];
  
  void makeCheckImage(void) {
  
    int i, j, c;
  
    for (i = 0; i &lt; CHECK_IMAGE_HEIGHT; i++)
  
      for (j = 0; j &lt; CHECK_IMAGE_WIDTH; j++) {
  
        checkImage[i][j][0] = (GLubyte) 255;
        checkImage[i][j][1] = (GLubyte) i == j ? 255 : 0;
        checkImage[i][j][2] = (GLubyte) 255;
  
      }
  
  }
  
  void init() {
    glClearColor(0.0, 0.0, 0.0, 0.0);
    glShadeModel(GL_FLAT);
    makeCheckImage();
    glPixelStorei(GL_UNPACK_ALIGNMENT, 1);
  }
  
  void display() {
    glClear(GL_COLOR_BUFFER_BIT);
    glRasterPos2i(0, 0);
    glDrawPixels(CHECK_IMAGE_WIDTH, CHECK_IMAGE_HEIGHT, GL_RGB, GL_UNSIGNED_BYTE, checkImage);
    glFlush();
  }
  
  void reshape(int w, int h) {
    gluOrtho2D(-10.0f, 10.0f, -10.0f, 10.0f);
    glViewport(0, 0, w, h);
  }
  
  int main(int argc, char **argv) {
    glutInit(&amp;argc, argv);
    glutInitDisplayMode(GLUT_RGB);
    glutCreateWindow(argv[0]);
    glutDisplayFunc(display);
    glutReshapeFunc(reshape);
    glutMainLoop();
    return 0;
  }
  </code></pre>