title: glReadPixels with screen pixels
body: <p>I am trying to read the RGB value of a screen pixel doing:</p>
  
  <pre><code>#include "stdafx.h"
  #include&lt;windows.h&gt;
  #include&lt;stdio.h&gt;
  #include &lt;gl\GL.h&gt;
  
  int main(int argc, char** argv)
  {
      GLubyte color[3];
      glReadPixels(800, 800, 1, 1, GL_RGB, GL_UNSIGNED_BYTE, &amp;color);
  
      printf("R:%d G:%d B:%d", color[0], color[1], color[2]);
  
      while (1);
  
  }
  </code></pre>
  
  <p>But it doesn't matter which coordinates I ask for. It always returns me R:204 G:204 B:204</p>
  
  <p>What am I doing wrong?</p>